WO2021147436A1 - Bi/er/la/al co-doped l-band or c+l-band quartz optical fiber and preparation method therefor - Google Patents

Abstract

A Bi/Er/La/Al co-doped L-band or C+L-band quartz optical fiber and a preparation method therefor. The optical fiber consists of a core (1), an inner cladding (2) and a cladding (3), the core (1) being made of quartz doped with GeO ₂, the inner cladding (2) being made of a Bi/Er/La/Al ion co-doped material, and the cladding (3) being made of pure quartz. Different doping ions are deposited alternately by using a high temperature doping-based modified chemical vapor deposition (MCVD) technique and an atomic layer deposition (ALD) technique, and the deposition thickness is 10 nm to 2000 nm. The optical fiber has the advantages of controllable doping concentration, uniform doping components, strong fluorescence intensity, wide gain spectrum and high gain, and has a wide application prospect in the fields of broadband optical fiber communication transmission, light amplification and light sensing, etc.

Description

Bi/Er/La/Al co-doped L-band or C+L-band quartz optical fiber and preparation method thereof Technical field

The invention belongs to the technical field of optical fibers, and more specifically relates to a Bi/Er/La/Al co-doped silica optical fiber and a preparation method thereof.

Background technique

With the rapid development of optical fiber communication technology and the continuous increase of communication capacity, people's demand for communication bandwidth and capacity is getting higher and higher. Especially in recent years, the rapid growth of 5G services and the application of the Internet of Things and cloud computing have led to limited transmission capacity and severe bandwidth shortages in the Internet under the influence of the environment, and even a "capacity crisis" has occurred. Therefore, the network architecture of the high-credibility next-generation Internet requires a communication system with ultra-high speed, ultra-bandwidth, and ultra-large capacity. The conventional wavelength division multiplexing (WDM) and optical fiber amplifiers combined technical solutions are increasingly showing their limitations; and the continuous reduction of the DWDM channel spacing, for multiplexing and demultiplexing technologies The difficulty is getting bigger and bigger. Although the erbium-doped fiber amplifier realizes the C-band optical relay amplification of the optical fiber communication system, which greatly promotes the development of optical fiber communication in the direction of all-optical transmission, the gain bandwidth of the erbium-doped fiber is only 35nm, which only covers the limited low-loss window of the silica fiber A small part of it is no longer able to meet the needs of users.

Broadening the gain spectrum of the erbium-doped fiber to the L-band can achieve more wave number multiplexing and demultiplexing, which will have important application value for ultra-wideband optical signal transmission. The present invention is based on high-temperature doping-modified chemical vapor deposition (MCVD) and atomic layer deposition (ALD). A large number of experimental studies have been carried out on L-band or C+L-band gain fibers, achieving wide bandwidth, high gain, and high-speed The development of optical fiber communication and the application of optical fiber sensing are of great significance.

Summary of the invention

The purpose of the present invention is to improve the advantages of chemical vapor deposition or atomic layer deposition technology based on high-temperature doping, combining bismuth oxide, erbium oxide and lanthanum oxide nanomaterials with optical fiber preparation to provide a Bi/Er/La/Al co- L wave band or C+L wave band doped silica optical fiber and preparation method thereof. There is energy transfer between Bi ions and Er ions, which can improve pump absorption efficiency; adding Al element to Er-doped fiber can increase the concentration of Er, and promote the formation of Stark splitting of Er energy level, which makes the absorption of Er-doped fiber The cross-section and emission cross-section are broadened. At the same time, this patent adopts the co-doping of the four elements Bi/Er/La/Al, and the choice of La as the co-dopant is because it is the element with the smallest molecular weight among the lanthanides, and its 4f electron layer does not electronic. Therefore, La is optically inactive, has no absorption peak in the optical communication band, and has almost no effect on the absorption and emission cross sections of Er. At the same time, La has a certain contribution to improving the refractive index. Er / La-doped fiber at 1550nm were still level ⁴ I _13/2 - ⁴ I _15/2 transition between. La, like other rare earth elements in Er-doped fibers, occupies the gap position in the Si network. When Er element and La element are doped into the fiber core layer together, if the number of La ions is large enough, several La ions are surrounded by one Er ion to increase the distance between Er ions to avoid Er ions from occurring Agglomeration phenomenon, so as to achieve high concentration of Er ions doping. In high-concentration Er-doped fiber, after Er ions absorb the pump light, C-band ASE is first generated at the front end of the Er fiber, and the C-band ASE generated is absorbed by Er ions in the back-end fiber as the secondary pump source. Thereby forming the L-band ASE spectrum. The doped fiber has the characteristics of low background loss, high Er ion doping concentration, strong fluorescence intensity, wide 3dB gain spectrum in the L-band, strong gain, simple structure, and easy industrialization. It can be used for broadband optical fiber communication transmission and amplification. It will be of great significance to the development of high-speed optical fiber communications.

In order to achieve the above objective, the present invention adopts the following technical solutions:

One kind of Bi / Er / La / Al codoped L-band or C + L band quartz optical fiber comprising a core, an inner cladding and a cladding, the core is a GeO ₂ doped silica constituting the high refractive index, the The inner cladding layer is composed of Bi/Er/La/Al ion co-doped material, the cladding layer is composed of pure quartz material, and the inner cladding layer wraps the core and is located in the middle of the cladding layer.

The core layer doped ions are bismuth ions Bi ⁰ , Bi ⁺ , Bi ³⁺ , Bi ⁵⁺ , erbium ions Er ³⁺ , lanthanum ions La ³⁺ , aluminum ions Al ³⁺ and germanium dioxide with improved refractive index distribution .

The inner cladding layer is formed by alternately depositing an appropriate amount of Bi/Er/La/Al co-doped material using a high-temperature doping modified chemical vapor deposition method or an atomic layer deposition technique, and the deposition thickness is 10-2000 nm.

The core diameter is 5.0-20.0 μm, the inner cladding diameter is 8.0-50.0 μm, and the cladding diameter is 40.0-400.0 μm.

The core and the inner cladding layer can be integrated into a Bi/Er/La/Al co-doped core layer structure.

The core layer has a diameter of 5.0 to 80.0 μm, the cladding diameter is 60.0 to 400.0 μm, the refractive index difference between the core layer and the cladding layer is between 0.3% and 5.5%, and the cladding shape is circular, quadrilateral, and hexagonal. Shaped or octagonal.

The absorption peaks of the optical fiber are respectively 500±40,700±20,800±20, 1000±40 and 1480±20nm; the L-band 3dB fluorescence spectrum range is between 1565 and 1630nm; the C+L-band 3dB fluorescence spectrum range is between 1530nm and 1625nm Time; the gain size is 10 ~ 35dB.

The fiber can be applied to L-band (1565-1625nm) or C+L-band (1530nm-1625nm) active optical amplifier fiber, active single polarization maintaining fiber, active high-order optical vortex amplifier fiber (order 2-6) , Fiber lasers (including continuous, pulsed and tunable lasers), and wide-spectrum light sources in the L-band or C+L band (including mode fibers, 2-6-order few-mode fibers, and 2-6-order optical vortex light sources).

A method for preparing Bi/Er/La/Al co-doped L-band or C+L-band active silica fiber, the steps are as follows:

1) Using an improved chemical vapor deposition method, that is, MCVD to deposit a loose layer of silicon dioxide, and process it at a high temperature to a semi-transparent vitrified state, which is the cladding;

2) Then, using MCVD high temperature doping or atomic layer deposition technology to uniformly deposit bismuth oxide, erbium oxide, lanthanum oxide and aluminum oxide materials on the surface of the cladding layer, which is the inner cladding layer;

3) Deposition of germanium dioxide, the concentration is controlled at 1.0-15.0 mol%, and the loose layer doped with germanium dioxide is semi-vitrified to become the core layer;

4) Adjust the doping concentration and dopant particle distribution of bismuth oxide, erbium oxide, lanthanum oxide and aluminum oxide by repeating the cycle of step 2);

5) The optical fiber preform is obtained by using the MCVD high temperature shrink rod, and finally, the doped optical fiber preform is drawn.

Compared with the prior art, the present invention has the following obvious substantive features and significant advantages:

1. Bi/Er/La/Al co-doped L-band or C+L-band quartz fiber can achieve high-gain wide-spectrum amplification in L-band or C+L-band, with a gain of 15-35dB;

2. Using high temperature doping to improve chemical vapor deposition or atomic layer deposition technology, with good uniformity, high doping concentration, convenient and feasible, so as to obtain higher quality Bi/Er/La/Al co-doped L-band or C+L Band quartz fiber;

3. The structure is simple, the price is low, and it is easy to industrialize. It can be used for broadband optical fiber communication transmission and amplification, and it will have great significance for the development of high-speed optical fiber communication.

Description of the drawings

Fig. 1 is a schematic diagram of two structures of the Bi/Er/La/Al co-doped L-band and C+L-band silica fibers of the present invention.

Among them, 1-core layer, 2-inner cladding layer, 3-cladding layer

Figure 2 is the fluorescence spectrum of the present invention in the L band.

Figure 3 is the fluorescence spectrum of the present invention in the C+L band.

Detailed ways

The present invention will be described in detail below with reference to the drawings and specific embodiments.

Example 1

Refer to Figure 1, a Bi/Er/La/Al co-doped L-band silica fiber, including a core 1, an inner cladding 2 and a cladding 3. The core 1 is made of a small amount of high refractive index GeO ₂ dioxide The inner cladding layer 2 is composed of Bi/Er/La/Al co-doped ion material, and the cladding layer 3 is composed of pure quartz material. First, deposit a loose layer of silicon dioxide and treat it at a high temperature to a semi-transparent vitrified state, which is the cladding layer 3. Secondly, use atomic layer deposition technology to uniformly deposit bismuth oxide, erbium oxide and lanthanum oxide materials on the surface of the cladding layer 3. Inner cladding layer 2, repeat the cycle to adjust the doping concentration of bismuth oxide, erbium oxide and lanthanum oxide and the distribution of doped particles, so that the deposition thickness is 200nm, and then germanium dioxide is deposited, the concentration is controlled to 5.0mol%, and the The loose layer doped with germanium dioxide is semi-vitrified, which is the core layer 1. Finally, the MCVD high temperature shrink rod is used to obtain the optical fiber preform, which is placed in the drawing tower for drawing to make Bi/Er/La/Al co-doped L-band silica fiber , The core diameter is 5.0 μm, the inner cladding diameter is 8.0 μm, and the cladding diameter is 120.0 μm. The fluorescence spectrum is shown in Figure 2.

Example 2

Refer to Figure 1, a Bi/Er/La/Al co-doped L-band or C+L-band silica fiber, including core 1, inner cladding 2, and cladding 3. The core 1 is doped with a small amount of high refractive index GeO ₂ is composed of a loose silicon dioxide layer, the inner cladding layer 2 is composed of Bi/Er/La/Al co-doped material, and the cladding layer 3 is composed of pure quartz material or doped with fluorine ions to reduce a small amount of refractive index. First, deposit a loose layer of silicon dioxide, or a loose layer of fluorine-doped silicon dioxide, and process it at a high temperature to a semi-transparent vitrified state, which is the cladding layer 3. Secondly, use MCVD high-temperature doping technology to combine bismuth oxide, erbium oxide and oxidation The lanthanum material is uniformly deposited on the surface of the cladding layer 3, which is the inner cladding layer 2. The cycle is repeated to adjust the doping concentration of bismuth oxide, erbium oxide and lanthanum oxide and the distribution of doped particles, so that the deposition thickness is 500nm, and then the deposition of dioxide The concentration of germanium is controlled to 3.0 mol%, and the loose layer doped with germanium dioxide is semi-vitrified to become core layer 1. Secondly, the end of the deposition of the core layer will be at the end; finally, the optical fiber preform is obtained by MCVD high temperature shrinking rod, Placed in the drawing tower for wire drawing to produce Bi/Er/La/Al co-doped L-band or C+L-band silica fiber, characterized by a core diameter of 6.0μm, an inner cladding diameter of 10.0μm, and a cladding diameter of 130.0 μm.

Example 3

Refer to Figure 1(b), a Bi/Er/La/Al co-doped C+L band silica fiber, including a core layer and a cladding layer 3. The core layer is made of silica _{doped with a small amount of high refractive index GeO 2} The loose layer is composed of Bi/Er/La co-doped ions, wherein the Bi/Er/La/Al co-doped ions are deposited by atomic layer deposition technology; the cladding layer 3 is composed of pure quartz material with a lower refractive index than the core layer , And finally shrink into a rod drawing. Among them, the Bi/Er/La/Al co-doped L-band silica fiber is characterized in that the core diameter is 10.0μm, the inner cladding diameter is 120.0μm, the refractive index difference between the core and the cladding is 0.69%, and the cladding is circular . After the doped fiber is pumped by the 980nm, 1480nm laser dual pump system, its fluorescence spectrum is shown in Figure 3.

Example 4

See Figure 1(b), a Bi/Er/La/Al co-doped L-band or C+L-band silica fiber, including a core layer and a cladding layer 3. The core layer is doped with a small amount of high refractive index GeO ₂ The loose layer of silicon dioxide is composed of Bi/Er/La/Al co-doped ions. Among them, Bi/Er/La/Al co-doped ions are deposited by MCVD high-temperature doping technology; the cladding layer 3 is made of a higher refractive index than the core layer. It is composed of low-grade pure quartz or fluorine-doped pure quartz material; finally, it is shrunk into a rod drawing. Among them, the Bi/Er/La/Al co-doped L-band or C+L-band silica fiber is characterized in that the core diameter is 12.0μm, the inner cladding diameter is 130.0μm, and the refractive index difference between the core layer and the cladding layer is 0.77%. The cladding is round.

Claims (9)

1. A Bi/Er/La/Al co-doped L-band or C+L-band quartz optical fiber, comprising a core (1), an inner cladding (2), and a cladding (3), characterized in that the core (1) ) Is composed of GeO ₂ doped quartz, the inner cladding layer (2) is composed of Bi/Er/La/Al ion co-doped material, the cladding layer (3) is composed of pure quartz material, and the inner cladding layer (3) is composed of pure quartz material. The layer (2) wraps the core (1) and is located in the middle of the cladding (3).
2. The Bi/Er/La/Al co-doped L-band or C+L-band silica fiber according to claim 1, wherein the core (1) and the inner cladding (2) are integrated into Bi/Er/La /Al co-doped core layer structure.
3. The Bi/Er/La/Al co-doped L-band or C+L-band silica optical fiber according to claim 2, wherein the core layer doped ions are bismuth ions Bi ⁰ , Bi ⁺ , Bi ³⁺ , Bi ⁵⁺ , erbium ion Er ³⁺ , lanthanum ion La ³⁺ , aluminum ion Al ³⁺ and germanium dioxide with improved refractive index distribution.
4. The Bi/Er/La/Al co-doped L-band or C+L-band silica fiber according to claim 1, wherein the inner cladding (2) is an improved chemical vapor deposition technology and a high-temperature doping system Atomic layer deposition technology alternately deposits appropriate amounts of Bi/Er/La/Al co-doped materials with a deposition thickness of 10-2000nm; or an improved chemical vapor deposition technology with high-temperature doped metal organic system to deposit various doped Bi, Er, La, Al ions; or use external vapor deposition technology (OVD) to deposit various doped Bi, Er, La, Al ions, or solution doping technology combined with improved chemical vapor deposition; the Bi ion concentration range is controlled within 0.01- 1.5mol%; Er ion concentration range is controlled within 0.05-15.0mol%; La and Al ion concentration range is controlled within 0.1-15.0mol%.
5. The Bi/Er/La/Al co-doped L-band or C+L-band silica fiber according to claim 1, wherein the diameter of the core (1) is 3.0-20.0 μm, and the diameter of the inner cladding (2) It is 6 to 50.0 μm, and the diameter of the cladding (3) is 40.0 to 400.0 μm.
6. The Bi/Er/La/Al co-doped L-band or C+L-band silica fiber according to claim 2, wherein the diameter of the core layer is 5.0-80.0 μm, and the diameter of the cladding (3) is 60.0～400.0μm, the refractive index difference between the core layer and the cladding layer (3) is between 0.3% and 5.5%. The outer cladding layer of the optical fiber is a single cladding or double cladding structure. The shape of the double cladding includes elliptical and D-shaped , Quadrilateral, hexagonal or octagonal structure, etc. At the same time, the L-band range is mainly concentrated in the 1565-1625nm band, and the C+L-band range is mainly concentrated in the 1530nm-1625nm band.
7. The Bi/Er/La/Al co-doped L-band or C+L-band silica fiber according to any one of claims 1-6, characterized in that: the optical fiber can be applied to active L-band or C+L-band Optical amplifier fiber, active single polarization maintaining fiber, active high-order optical vortex amplifier fiber and fiber laser (including first-order, second-order, third-order, fourth-order, fifth-order, and sixth-order few-mode optical amplification and vortex optical amplification and corresponding High-order fiber lasers).
8. The Bi/Er/La/Al co-doped L-band or C+L-band silica fiber according to any one of claims 1-6, characterized in that: the fiber can pass a 980nm laser dual pump system or a 980nm and 1480nm laser The dual-pump system obtains the L-band or C+L-band ultra-wide-spectrum fluorescence spectrum, and the corresponding L-band or C+L-band ultra-wide-spectrum light source and tunable laser.
9. A method for preparing Bi/Er/La/Al co-doped L-band or C+L-band silica fiber, which is characterized in that the steps are as follows:

   1) Use improved chemical vapor deposition (MCVD) to deposit a loose layer of silicon dioxide, and process it at a high temperature to a semi-transparent vitrified state, which is the cladding layer (3);

   2) Then, use MCVD high temperature doping or atomic layer deposition doping technology or solution doping technology to uniformly deposit bismuth oxide, erbium oxide, lanthanum oxide and aluminum oxide on the surface of the cladding layer (3), which is the inner cladding layer (2) ；

   3) Deposit germanium dioxide with a concentration of 1 to 15.0 mol%, and semi-vitrify the loose layer doped with germanium dioxide to become the core layer (1);

   4) Adjust the doping concentration and doping particle distribution of bismuth oxide, erbium oxide, lanthanum oxide and aluminum oxide by repeating the cycle of step 2);

   5) The optical fiber preform is obtained by using the MCVD high temperature shrink rod, and finally, the doped optical fiber preform is drawn into L-band or C+L-band silica fiber.

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