CN118795588A - A doped optical fiber and related equipment - Google Patents

Abstract

The embodiment of the application discloses a doped optical fiber and related equipment, which are used for realizing mode field matching with a communication optical fiber. The doped optical fiber provided by the embodiment of the application comprises a fiber core and an outer cladding which are sequentially arranged from inside to outside; the fiber core is doped with rare earth ions; the refractive index between the fiber core and the outer cladding is delta core, and the radius of the fiber core is r core; Δcore and r core satisfy the following relationship: 0.012 μm.ltoreq.Δcore-r core is less than or equal to 0.048 mu m.

Description

A doped optical fiber and related equipment

Technical Field

The embodiments of the present application relate to the field of optical communications, and in particular to a doped optical fiber and related equipment.

Background Art

Doped fiber amplifier is a commonly used optical amplifier. It amplifies signal light by absorbing the energy of pump light and converting it into signal light energy.

In order to improve the pumping efficiency of the doped fiber amplifier, the core size of the doped fiber is usually smaller, generally smaller than the core size of the communication fiber, which results in a mismatch between the mode field of the doped fiber and the mode field of the communication fiber.

Mode field mismatch leads to large insertion loss in the fusion splicing/butt connection between the doped optical fiber and the communication optical fiber, which increases the power attenuation of the pump light and the signal light and affects the signal amplification effect.

Summary of the invention

The embodiments of the present application provide a doped optical fiber and related equipment for achieving mode field matching with a communication optical fiber.

In a first aspect, an embodiment of the present application provides a doped optical fiber. The doped optical fiber includes a core and an outer cladding arranged in sequence from the inside to the outside. The core is doped with rare earth ions. If the relative refractive index difference between the core and the outer cladding is Δcore, and the radius of the core is rcore; then Δcore and rcore satisfy the following relationship: 0.012μm≤Δcore*rcore≤0.048μm.

In the embodiment of the present application, the product of Δcore and r core of the doped optical fiber is limited to between 0.012 μm and 0.048 μm, so that the mode field of the doped optical fiber can be matched with the mode field of the communication optical fiber (for example, the mode field diameter at a wavelength of 1310 nm is 8.2 μm-9.9 μm, which is a commonly used mode field range for communication optical fibers). By matching the mode field, the fusion splicing insertion loss/butt insertion loss between the doped optical fiber and the communication optical fiber is reduced, thereby limiting the power attenuation of the pump light and the signal light, and ensuring the signal amplification effect.

In an optional implementation, an inner cladding and a depressed layer are further included between the core and the outer cladding. The doped optical fiber is sequentially arranged with a core, an inner cladding, a depressed layer and an outer cladding from the inside to the outside. In this structure, Δcore and rcore satisfy: 0.4%≤Δcore≤0.8%, 3.5μm≤r core≤5.5μm.

In the embodiment of the present application, under the premise of matching the mode field of the doped optical fiber with that of the communication optical fiber, the additional bending loss of the doped optical fiber is reduced by designing the depression layer. This can improve the macrobending performance of the doped optical fiber (i.e., the ability of the optical fiber to resist bending) and reduce the attenuation loss of the doped optical fiber. This allows the doped optical fiber to have lower losses even in bending, winding, and other scenarios, thereby ensuring the signal amplification effect in these scenarios.

In an optional implementation, if the relative refractive index difference between the inner cladding and the outer cladding is Δcladding 1, and the width of the inner cladding is a; then Δcladding 1 and a satisfy: -0.1%≤Δcladding 1≤0.1%, a≤6μm.

In the embodiment of the present application, by limiting Δcladding 1 and a within the above range, the optical fiber can be placed in the optimal anti-bending performance region.

In an optional implementation, if the relative refractive index difference between the depressed layer and the outer cladding is Δcladding 2, and the width of the depressed layer is b; then Δcladding 2 and b satisfy: -0.5%≤Δcladding 2≤-0.1%, 4μm≤b≤16μm.

In the embodiment of the present application, Δcladding 2 and b are limited to the above ranges, so that the bending loss can be reduced as much as possible within the scope of process limitations.

In an optional implementation, Δcore and r core satisfy: 0.4%≤Δcore≤0.8%, 4.2 μm≤rcore≤4.8 μm.

In the embodiment of the present application, Δcore and r core are limited to the above ranges, which can further ensure that the mode field of the doped optical fiber falls within the range of the communication optical fiber mode field, thereby ensuring mode field matching with the communication optical fiber.

In an optional implementation, the rare earth ions doped in the fiber core include at least one of the following: erbium Er, bismuth Bi, ytterbium Yb, and thulium Tm.

In the embodiment of the present application, by doping with the above-mentioned rare earth elements, amplification of signals in different bands can be achieved (for example, doping erbium ions in the fiber core can achieve amplification of C-band and L-band signals, and doping bismuth ions can achieve amplification of O-band signals).

In an optional implementation, the fiber core includes a first core layer and a second core layer arranged in sequence from the inside to the outside, and the doping concentrations of rare earth ions in the first core layer and the second core layer are different.

In the embodiment of the present application, the doping concentrations of different layers of the fiber core are different, which can control the amplification effects of signals in different bands, thereby matching the signal amplification requirements in different scenarios.

In an optional implementation, the rare earth ion doping concentration of the first core layer is higher than that of the second core layer. The second core layer is doped with a target dopant, which is used to increase the refractive index of the second core layer.

In the embodiment of the present application, since the smaller the wavelength of the signal, the smaller the mode field of the light field, and the more the energy is concentrated in the center of the core, the doping concentration of the inner layer of the core (the first core layer) is higher than that of the outer layer (the second core layer), which can ensure the amplification effect of the short-wavelength band signal (such as the C-band signal), thereby improving the gain in the short-wavelength band (such as the C-band). In addition, by increasing the refractive index of the outer layer of the core (the second core layer) through the target dopant, the refractive index of the entire core can be made flatter, thereby ensuring that the signal light is transmitted in the optical fiber in the fundamental mode.

It is worth noting that in the embodiments of the present application, long wavelength and short wavelength are relative concepts. For example, the wavelength of the C band is shorter than that of the L band, and longer than that of the O band. Then the C band is a short wavelength band relative to the L band (the L band is a long wavelength band relative to the C band), and is a long wavelength relative to the O band (the O band is a short wavelength band relative to the C band).

In an optional implementation, the radius of the first core layer is r1, 2 μm≤r1≤4 μm.

In an embodiment of the present application, the radius of the first core layer is limited to 2μm-4μm, so that the area with high doping concentration can better match the C-band signal, improve the gain in the C-band, and play a role in gain balance between different bands (for example, between the C-band and the L-band).

In an optional implementation, the rare earth ion doping concentration of the second core layer is higher than that of the first core layer. The first core layer is doped with a target dopant, which is used to increase the refractive index of the first core layer.

In the embodiment of the present application, the structure in which the doping concentration of the outer layer (second core layer) of the core is higher than that of the inner layer (first core layer) is called a ring-doped structure. Since the ring-doped structure can increase the mode field overlap between the long-wavelength band signal (such as the L-band signal) and the pump light, the use of the ring-doped structure can improve the gain in the long-wavelength band (such as the L-band). Thus, when the optical fiber simultaneously transmits multi-band signals (such as the C-band signal + the L-band signal), gain balance between different bands is achieved. In addition, by increasing the refractive index of the inner layer (first core layer) of the core through the target dopant, the refractive index of the entire core can be made flatter to ensure that the signal light is transmitted in the optical fiber in the fundamental mode.

In an optional implementation, the radius of the first core layer is r2, 0 μm≤r2≤2 μm.

In the embodiment of the present application, the radius of the first core layer is limited to 0μm-2μm, and the distance between the innermost end of the second core layer and the center of the core can be limited to 0μm-2μm. This size design can make the area with high doping concentration better match the signal of the long wavelength band (such as L-band signal), and enhance the amplification effect of the signal of the long wavelength band (such as L-band signal). Thereby, the gain of the long wavelength band is increased and the gain of the short wavelength band is weakened, achieving the gain balance of long and short wavelengths, which is suitable for the transmission scenario of multi-band signal light.

Optionally, in the O-band + C-band transmission scenario of bismuth-doped optical fiber, the gain of the C-band can be increased and the gain of the O-band can be weakened through a ring-shaped doping structure, thereby achieving gain balance between the O-band and the C-band.

In a second aspect, an embodiment of the present application provides an optical communication device, wherein the optical communication device comprises the doped optical fiber described in the first aspect, and the doped optical fiber is used to transmit an optical signal.

In a third aspect, an embodiment of the present application provides an optical communication system. The optical communication system includes: a pump light source, a communication optical fiber and a doped optical fiber. Among them, the doped optical fiber is the optical fiber described in the first aspect. The communication optical fiber and the doped optical fiber are interconnected to transmit signal light. The pump light source is connected to the doped optical fiber, and the pump light emitted by the pump light source is input into the doped optical fiber. The doped optical fiber is used to absorb the energy of the pump light and amplify the signal light.

In an optional implementation, the communication optical fiber is G657 optical fiber and/or G652 optical fiber.

The beneficial effects of the second and third aspects refer to the first aspect and will not be repeated here.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of an optical communication system provided in an embodiment of the present application;

FIG2 is a schematic diagram of the structure of a doped optical fiber provided in an embodiment of the present application;

FIG3 is a schematic diagram of the structure of a doped optical fiber including a depressed layer provided in an embodiment of the present application;

FIG4 is a schematic diagram of simulation results of a doped optical fiber including a depressed layer provided in an embodiment of the present application;

FIG5 is a schematic diagram of simulation results of a doped optical fiber including a depressed layer provided in an embodiment of the present application;

FIG6 is a schematic diagram of the structure of a fiber core with a high inner layer doping concentration provided in an embodiment of the present application;

FIG7 is a schematic diagram of different core layer inversion efficiencies provided by an embodiment of the present application;

FIG8 is a schematic diagram of the structure of a fiber core with a high outer layer doping concentration provided in an embodiment of the present application;

FIG9 is a schematic diagram of mode fields of signals of different bands provided in an embodiment of the present application;

FIG. 10 is a schematic diagram of the structure of an optical communication device provided in an embodiment of the present application.

DETAILED DESCRIPTION

The embodiments of the present application are described below in conjunction with the accompanying drawings. Those skilled in the art will appreciate that, with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged in appropriate circumstances, which is only to describe the distinction mode adopted by the objects of the same attribute in the embodiments of the present application when describing. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, so that the process, method, system, product or equipment containing a series of units need not be limited to those units, but may include other units that are not clearly listed or inherent to these processes, methods, products or equipment. In addition, "at least one" refers to one or more, and "multiple" refers to two or more. "And/or", describes the association relationship of associated objects, indicating that three relationships can exist, for example, A and/or B, can represent: A exists alone, A and B exist simultaneously, and B exists alone, wherein A, B can be singular or plural. The character "/" generally represents that the associated objects before and after are a kind of "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c can mean: a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

The doped fiber amplifier is used to amplify optical signals. Specifically, the doped fiber amplifier includes a doped fiber and a pump light source. The pump light source is used to provide pump light, and the doped fiber converts the energy of the pump light into the energy of the signal light to achieve amplification of the signal light.

Since the pump light source needs to be connected to a power supply, the doped fiber amplifier containing the pump light source can only be deployed in the machine room. Therefore, in the optical communication system, it is impossible to deploy the doped fiber amplifier to amplify the optical signal at a location far away from the machine room, which limits the application scope of the doped fiber amplifier.

In order to solve the above problems, an embodiment of the present application provides an optical communication system in which a pump light source and a doped optical fiber can be deployed at different locations, thereby improving the flexibility of the deployment location of the doped optical fiber amplifier and expanding the application range of the doped optical fiber amplifier.

As shown in FIG1 , the optical communication system provided in the embodiment of the present application includes: a transmitting device, a pump light source, a combiner, a communication optical fiber, a doped optical fiber 2000, and a receiving device. Among them, the transmitting device is used to emit signal light, the pump light source is used to emit pump light, and the combiner is used to combine the signal light with the pump light. The combined signal is input into the communication optical fiber and transmitted to the doped optical fiber 2000 via the communication optical fiber. The doped optical fiber 2000 is used to absorb the energy of the pump light and convert it into the energy of the signal light to amplify the signal light. The amplified signal light is transmitted to the receiving device.

Optionally, the optical communication system may be a transmission network, an access network, etc., which is not limited in this application.

Optionally, the sending device in FIG. 1 may be an optical line terminal (OLT) device, and the receiving device may be an optical network terminal (ONT) device, which is not limited in the present application.

Optionally, the wave combining device in FIG. 1 may be a wavelength division multiplexer (WDM), a coupler, etc., which is not limited in the present application.

Optionally, the pump light source can be deployed outside the transmitting device as shown in FIG. 1 , or it can be deployed inside the transmitting device (correspondingly, the combiner device is also deployed inside the transmitting device), and this application does not limit this.

In the embodiment of the present application, the doped optical fiber 2000 can be deployed at any position of the optical communication system. For example, it is deployed in front of the receiving device shown in FIG1, in the wave combiner shown in FIG1, in the passive optical device (filter, splitter, etc.), on the street side of the customer side, at the edge end in the user corridor, in the home optical fiber, in the client optical fiber, in the receiving device (such as ONT), or in the transmission optical cable at any position, which is not limited by the present application.

In the embodiment of the present application, the pump light source and the doped optical fiber are deployed at different positions of the optical communication system. For example, the pump light source that needs to be connected to the power supply is deployed in the machine room (such as the OLT machine room), and the doped optical fiber 2000 is deployed at any position in the system. The doped optical fiber 2000 can amplify the signal light through the pump light at any position in the system, thereby expanding the application scope of the doped optical fiber amplifier from the machine room to the entire optical communication system, thereby expanding the application scope of the doped optical fiber amplifier.

Optionally, in the optical communication system structure provided in the embodiment of the present application, if the doped optical fiber 2000 is deployed at the user end side far away from the machine room (for example, near the receiving device or ONT), the signal can be amplified at the user end side where the traditional doped optical fiber amplifier cannot be deployed, thereby improving the signal power at the user end side. Optionally, the pump light source can also be deployed together with the doped optical fiber, which is not limited in the present application.

In the optical communication system shown in FIG. 1 , in addition to the transmitting device, the signal light may also come from other devices, such as a scheduling device, a relay amplification device, etc. in the system, and this application does not limit this.

In the optical communication system shown in FIG. 1 , in addition to the receiving device, the signal light can also be input to other devices, such as a scheduling device, a relay amplification device, etc. in the system, and this application does not limit this.

In the system shown in Fig. 1, the structure of the doped optical fiber 2000 may be as shown in Fig. 2. As shown in Fig. 2a, the doped optical fiber 2000 includes a core 2100 and an outer cladding 2200 arranged sequentially from the inside to the outside.

The fiber core 2100 is doped with rare earth ions to absorb pump light and convert the energy of the pump light into the energy of signal light, thereby amplifying the signal light.

Optionally, the rare earth ions doped in the fiber core 2100 include at least one of the following: erbium Er, bismuth Bi, ytterbium Yb, and thulium Tm, which is not limited in the present application.

In the embodiment of the present application, by doping with the above-mentioned rare earth elements, amplification of signals in different bands can be achieved (for example, doping erbium ions in the fiber core can achieve amplification of C-band and L-band signals, and doping bismuth ions can achieve amplification of O-band signals).

The outer cladding 2200 may be pure silica, or may be made of other materials, such as silica glass containing a small amount of dopants, etc., which is not limited in the present application.

Figure b in Figure 2 is a relative refractive index difference distribution diagram of the doped optical fiber 2000. Among them, the horizontal axis is the distance d from the center of the optical fiber, and the vertical axis is the relative refractive index difference between the refractive index at this position and the refractive index of the outer cladding of the optical fiber. As shown in Figure b of Figure 2, the coordinates of the right corner are (r core, Δcore), indicating that the distance d between this point and the center of the optical fiber is rcore, and the relative refractive index difference is Δcore. From the center of the optical fiber to this point, the refractive index distribution is a horizontal straight line, indicating that the relative refractive index difference from the center of the optical fiber to any point r core away from the center of the optical fiber is Δcore.

In the embodiment of the present application, r core represents the radius of the core 2100, and Δ core represents the relative refractive index difference between the core 2100 and the outer cladding 2200. In FIG. 2 b, the relative refractive index difference between the core 2100 and the outer cladding 2200 is Δ core, and the refractive index of the core 2100 is Δ core + the refractive index of the outer cladding 2200.

In the doped optical fiber 2000 provided in the embodiment of the present application, the mode field range of the doped optical fiber 2000 can be limited to match the mode field of the communication optical fiber by limiting the size and relative refractive index difference of the core 2100. Specifically, 0.012 μm ≤ r core * Δ core ≤ 0.048 μm can be limited.

In the embodiment of the present application, the product of Δcore and r core of the doped optical fiber 2000 is limited to between 0.012 μm and 0.048 μm, so that the mode field of the doped optical fiber 2000 can be matched with the mode field of the communication optical fiber (for example, the mode field diameter at a wavelength of 1310 nm is 8.2 μm-9.9 μm, which is a commonly used mode field range for communication optical fibers). By matching the mode field, the fusion splicing insertion loss/butt insertion loss between the doped optical fiber 2000 and the communication optical fiber is reduced, thereby limiting the power attenuation of the pump light and the signal light, and ensuring the signal amplification effect.

If in the optical communication system shown in FIG1, the pump light source is deployed in the machine room, and the doped optical fiber 2000 is deployed on the user side far away from the machine room. Then the pump light from the pump light source in the machine room has a low power after being transmitted over a long distance to the doped optical fiber 2000, and the power of the signal light transmitted to the user side is also low. Through the structure of the doped optical fiber 2000 shown in FIG2, the fusion insertion loss/butt insertion loss between the doped optical fiber 2000 and the communication optical fiber can be reduced, thereby reducing the loss of the pump light and the signal light between the doped optical fiber 2000 and the communication optical fiber, increasing the power of the pump light and the signal light, and ensuring the signal amplification effect.

Optionally, Δcore and r core may satisfy: 0.4%≤Δcore≤0.8%, 4.2 μm≤r core≤4.8 μm.

In the embodiment of the present application, Δcore and r core are limited to the above ranges, which can further ensure that the mode field of the doped optical fiber falls within the range of the communication optical fiber mode field, thereby ensuring mode field matching with the communication optical fiber.

Optionally, the doped optical fiber 2000 provided in the embodiment of the present application can also improve the bending resistance by designing a depression layer. For example, as shown in Figure 3 a, a bending-resistant doped optical fiber 2000 provided in the embodiment of the present application includes: a core 2100, an inner cladding 2300, a depression layer 2400, and an outer cladding 2200 arranged in sequence from inside to outside.

The fiber core 2100 may be based on silica glass and doped with rare earth ions (such as erbium ions, bismuth ions, etc.) Optionally, the fiber core 2100 may also be doped with dopants such as aluminum (Al), phosphorus (P), lanthanum (La), and germanium (Ge).

Optionally, the fiber core 2100 can be prepared by modified chemical vapor deposition (MCVD).

The inner cladding 2300 tightly surrounds the core 2100 and may be pure silica or silica glass containing a small amount of dopants.

The depressed layer 2400 closely surrounds the inner cladding 2300, and the depressed layer 2400 may be fluorine (F)-doped silicon dioxide, or silicon dioxide doped with other dopants, and the dopants are used to reduce the refractive index of the depressed layer 2400. Optionally, the depressed layer 2400 may be prepared by MCVD, fluorine-doped sleeve, and the like.

Optionally, the depression layer 2400 may also reduce the refractive index by nanoparticle doping, air hole assistance, etc., which is not limited in the present application.

In this structure, Δcore and r core satisfy: 0.4%≤Δcore≤0.8%, 3.5μm≤r core≤5.5μm. (Optionally, the value range of r core can be further limited to 4μm≤r core≤5μm, which is not limited in this application)

In the embodiment of the present application, under the premise that the doped optical fiber 2000 matches the mode field of the communication optical fiber, the additional bending loss of the doped optical fiber 2000 is reduced by designing the depression layer 2400. Thus, the macrobending performance of the doped optical fiber 2000 (i.e., the ability of the optical fiber to resist bending) can be improved, and the attenuation loss of the doped optical fiber 2000 can be reduced. This allows the doped optical fiber 2000 to have lower losses even in bending, winding, and other scenarios, thereby ensuring the signal amplification effect in these scenarios.

For example, if the doped optical fiber 2000 is used in an access network, a home optical fiber, a client optical fiber, etc., the design of the depression layer 2400 can greatly reduce the additional bending loss in these scenarios and ensure the signal amplification effect.

Figure b in Figure 3 is a relative refractive index difference distribution diagram of the doped optical fiber 2000. Among them, r core is the radius of the core 2100, a is the width of the inner cladding, and b is the width of the depression layer. Among them, a refers to the width of the inner cladding 2300 itself, specifically the minimum distance between the outermost end and the innermost end of the inner cladding 2300, and does not refer to the distance between the inner cladding 2300 and the center of the doped optical fiber 2000. b is the same as the above, and will not be repeated here.

Herein, Δcore refers to the relative refractive index difference between the core 2100 and the outer cladding 2200 , Δcladding1 refers to the relative refractive index difference between the inner cladding 2300 and the outer cladding 2200 , and Δcladding 2 refers to the relative refractive index difference between the depression layer 2400 and the outer cladding 2200 .

In this refractive index distribution diagram, the horizontal axis is the distance d from the center of the optical fiber, and the vertical axis is the relative refractive index difference with the outer cladding 2200. Taking the second horizontal line on the right side of the vertical axis in Figure b of Figure 3 as an example, the horizontal axis of this line is from rcore to rcore+a, indicating that the distance d from the center of the optical fiber is from rcore to rcore+a (i.e., the point of the inner cladding 2300); the vertical axis of this line is the relative refractive index difference between the inner cladding 2300 and the outer cladding 2200. In other words, the refractive index distribution of the inner cladding 2300 is a horizontal straight line, indicating that at any point in the inner cladding 2300, the relative refractive index difference with the outer cladding is the same, which is Δcladding 1.

In the embodiment of the present application, Δcladding 1 and a can satisfy: -0.1%≤Δcladding 1≤0.1%, a≤6 μm. By limiting the above parameters, the optical fiber can be placed in the optimal anti-bending performance region.

In the embodiment of the present application, Δcladding 2 and b can satisfy: -0.5%≤Δcladding 2≤-0.1%, 4μm≤b≤16μm. By limiting the above parameters, the bending loss can be reduced as much as possible within the process limitation.

By selecting an optical fiber with a parameter within the size range and relative refractive index difference range defined in the embodiment of the present application for testing, a refractive index distribution profile as shown in FIG4 can be obtained (FIG. 4 is one of the embodiments of FIG3). FIG5 is a schematic diagram of the mode field and intensity distribution at the simulation 1310 of the refractive index distribution structure of FIG4.

The optical fiber mode field obtained by testing and simulating any parameters within the range meets the following conditions: the mode field diameter at 1310nm is (8.6-9.5)±0.4μm. Correspondingly, the mode field diameter at 1550nm is (9-11)±0.4μm.

For example, the simulation results of FIG. 5 show that the mode field diameter of the optical fiber at a wavelength of 1310 nm is 8.7 μm, and the mode field diameter at a wavelength of 1550 nm is 9.3 μm, which matches the mode field range of the communication optical fiber and achieves the expected matching target in the embodiment of the present application.

Optionally, several values are selected within the value range of the above parameters (such as r core, △ cladding 1, etc.) for simulation, and the mode field diameters at different wavelengths are shown in Table 1.

Table 1 Dimensions, refractive index and corresponding performance parameters of doped optical fiber 2000

From the results in Table 1, it can be seen that the mode field diameter of the doped fiber 2000 obtained by randomly selecting parameters within the range is between 8.27μm and 9.69μm at 1310nm and between 8.96μm and 10.54μm at 1550nm, which matches the mode field range of communication optical fiber.

The doped optical fiber 2000 shown in FIG3 is measured, and the measured results show that at 1625 nm, the additional bending loss of the optical fiber is less than or equal to 1 dB for 10 turns around a bending radius of 15 mm; and the additional bending loss is less than or equal to 1.5 dB for 10 turns around a bending radius of 10 mm. The results show that the optical fiber parameters of the doped optical fiber 2000 meet the requirements of the ITU-TG.657A standard and have excellent attenuation loss and macrobending performance.

In the embodiment of the present application, the amplification efficiency of optical signals in different wavelength bands can also be enhanced by different designs of the fiber core 2100. As shown in FIG6 , the fiber core 2100 can include a first core layer 2110 and a second core layer 2120 arranged sequentially from the inside to the outside, and the doping concentration of rare earth ions in the first core layer 2110 and the second core layer 2120 is different.

In the embodiment of the present application, the doping concentrations of different layers of the core are different, which can realize the control of the amplification effect of signals in different bands, thereby matching the signal amplification requirements in different scenarios. For example, since the smaller the wavelength of the signal, the smaller the mode field of the light field, and the more concentrated the energy is in the center of the core, as shown in FIG6, the doping concentration of the inner layer of the core (the first core layer 2110) is higher than that of the outer layer (the second core layer 2120), which can ensure the amplification effect of short-wavelength band signals (such as C-band signals), thereby improving the gain in the short-wavelength band (such as C-band).

It is worth noting that in the embodiments of the present application, long wavelength and short wavelength are relative concepts. For example, the wavelength of the C band is shorter than that of the L band, and longer than that of the O band. Then the C band is a short wavelength band relative to the L band (the L band is a long wavelength band relative to the C band), and is a long wavelength relative to the O band (the O band is a short wavelength band relative to the C band).

Optionally, as shown in FIG6 , a target dopant may be doped into the second core layer 2120. The target dopant is used to increase the refractive index of the second core layer 2120. This makes the overall refractive index of the fiber core 2100 smoother, ensuring that the light field is transmitted in the optical fiber in the fundamental mode.

In the fiber core 2100 shown in Fig. 6, the radius of the first core layer 2110 is r1, 2μm≤r1≤4μm. Limiting the radius of the first core layer 2110 to 2μm-4μm can make the high-doping concentration area better match the C-band signal and improve the amplification effect of the C-band signal.

In the embodiment of the present application, the core 2100 structure shown in FIG6 is also referred to as a local core doping structure. The intensity distribution of the light field in the core is shown by the arc in FIG7. The light field intensity is strongest in the central region close to the center of the core. The erbium ions in the central region can absorb enough pump light energy and realize laser amplification after transitioning to a high energy level. However, the erbium ions in the low inversion region (i.e., the region far from the center of the core) where the light field is weak will not only not amplify the laser, but will absorb the signal light energy. Therefore, making the doping concentration of the inner layer of the core higher than the doping concentration of the outer layer can make more erbium ions located in the center of the light field (i.e., the aforementioned central region), which is beneficial to improving the pumping efficiency.

It is worth noting that FIG6 and FIG7 take erbium-doped fiber as an example to describe the light field intensity distribution and local doping structure in the optical fiber, and do not limit the type of optical fiber to which the local doping structure is applicable. The local doping structure shown in FIG6 and FIG7 can also be applied to other types of optical fibers, such as bismuth-doped optical fibers, and this application does not limit this.

If the doped optical fiber 2000 including the core 2100 structure shown in FIG6 is applied in the optical communication system described in FIG1, the signal transmitted by the communication optical fiber in the optical communication system may include C-band signal light, and the amplification effect of the C-band signal is enhanced by this structure.

Optionally, if a bismuth-doped optical fiber including a local doping structure is applied in the optical communication system shown in FIG. 1 , the signal transmitted by the communication optical fiber in the optical communication system may include O-band signal light, and the amplification effect of the O-band signal is enhanced by the structure.

Optionally, as shown in FIG8 , the rare earth ion doping concentration of the second core layer 2120 may be higher than that of the first core layer 2110 , and a target dopant may be doped into the first core layer 2110 . The target dopant is used to increase the refractive index of the first core layer 2110 .

In the embodiment of the present application, the structure in which the doping concentration of the outer layer (second core layer) of the core is higher than that of the inner layer (first core layer) is called a ring-doped structure. Since the ring-doped structure can increase the mode field overlap between the long-wavelength band signal (such as the L-band signal) and the pump light, the use of the ring-doped structure can improve the gain in the long-wavelength band (such as the L-band). Thus, when the optical fiber simultaneously transmits multi-band signals (such as the C-band signal + the L-band signal), gain balance between different bands is achieved. In addition, by increasing the refractive index of the inner layer (first core layer) of the core through the target dopant, the refractive index of the entire core can be made flatter to ensure that the signal light is transmitted in the optical fiber in the form of a fundamental mode.

In the fiber core 2100 shown in FIG8 , the radius of the first core layer 2110 is r2, and 0 μm≤r2≤2 μm.

In the embodiment of the present application, the radius of the first core layer is limited to 0μm-2μm, and the distance between the innermost end of the second core layer and the center of the core can be limited to 0μm-2μm. This size design can make the area with high doping concentration better match the signal of the long wavelength band (such as L-band signal), and enhance the amplification effect of the signal of the long wavelength band (such as L-band signal). Thereby, the gain of the long wavelength band is increased and the gain of the short wavelength band is weakened, achieving the gain balance of long and short wavelengths, which is suitable for the transmission scenario of multi-band signal light.

In the embodiment of the present application, the core 2100 structure shown in FIG8 is also referred to as a ring-shaped doping distribution structure. Since the long-wave mode field is larger than the short-wave mode field under the same conditions, the use of a ring-shaped doping distribution structure can effectively increase the long-wave gain (such as the L band) and achieve a gain balancing effect between the long-wavelength band and the short-wavelength band. For example, as shown in FIG9, the mode field of the L band is larger than the mode field of the C band, and the gain balancing between the C band and the L band can be achieved through the ring-shaped doping structure.

If the doped optical fiber 2000 including the core 2100 structure shown in FIG8 is applied in the optical communication system described in FIG1, the signal transmitted by the communication optical fiber in the optical communication system may include L-band signal light, and the amplification effect of the L-band signal is enhanced by this structure.

Optionally, in the O-band + C-band transmission scenario of bismuth-doped optical fiber, the gain of the C-band can be increased and the gain of the O-band can be weakened through a ring-shaped doping structure to achieve gain balance between the O-band and the C-band. This application does not limit this.

Optionally, the fiber core 2100 shown in FIG. 6 or FIG. 7 may be prepared by using a modified chemical vapor deposition (MCVD) process.

It is worth noting that FIG. 6 or FIG. 8 is only an example of multi-layer doping of the fiber core 2100, and does not limit the relationship between the number of doping layers and the concentration. For example, the fiber core 2100 can be doped with 3 or more core layers with different doping concentrations. The specific doping concentration of each core layer is not limited. For example, the doping concentration of the core layer with a lower doping concentration can be 0 or non-0, and this application does not limit this.

In the embodiment of the present application, the fiber core 2100 may also be a non-layered fiber core. That is, the doping concentrations are the same everywhere inside the fiber core 2100. The local doping structure, the annular doping structure, and the non-layered doping structure of the fiber core 2100 are described above. It is worth noting that the embodiment of the present application may also protect the transition state between any two of the above three doping structures, such as the transition state between the annular doping structure and the non-layered doping structure, etc., and the present application does not limit this.

The doped optical fiber 2000 shown in any of the embodiments in FIG. 2 to FIG. 9 can be used as the doped optical fiber 2000 in the optical communication system shown in FIG. 1 to achieve amplification of the signal light. Optionally, the embodiment of the present application does not limit the position of the doped optical fiber 2000 in the system. The doped optical fiber 2000 can be in any optical device or at any position of the transmission optical fiber, and the present application does not limit this.

As shown in FIG10, an embodiment of the present application further provides an optical communication device 800. The optical communication device 800 includes the doped optical fiber 2000 shown in any embodiment of FIG2 to FIG10. Optionally, the optical communication device 800 may be an optical transmitting device, an optical amplifier, an optical line terminal, an optical receiving device, etc., which is not limited in the present application.

In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

Claims (13)

1. A doped optical fiber is characterized by comprising a fiber core and an outer cladding which are sequentially arranged from inside to outside;

the fiber core is doped with rare earth ions;

The relative refractive index difference between the core and the outer cladding is Δcore, the radius of the core is r core, and Δcore and r core satisfy the following relationship:

0.012μm≤Δcore*r core≤0.048μm。

2. the optical fiber of claim 1, further comprising an inner cladding and a depressed layer between the core and the outer cladding, the depressed layer between the inner cladding and the outer cladding;

Δcore and r core satisfy:

0.4％≤Δcore≤0.8％，3.5μm≤r core≤5.5μm。

3. the optical fiber of claim 2, wherein the relative refractive index difference between the inner cladding and the outer cladding is Δ cladding 1, the width of the inner cladding is a;

Δ cladding 1 and a satisfy:

-0.1％≤Δcladding 1≤0.1％，a≤6μm。

4. The optical fiber of claim 2 or 3, wherein the difference in relative refractive index between the depressed layer and the outer cladding is Δ cladding 2, the depressed layer having a width b;

Δ cladding 2 and b satisfy:

-0.5％≤Δcladding 2≤-0.1％，4μm≤b≤16μm。

5. The optical fiber of claim 1, wherein Δcore and r core satisfy:

0.4％≤Δcore≤0.8％，4.2μm≤r core≤4.8μm。

6. The optical fiber according to any one of claims 1 to 5, wherein the rare earth ions comprise at least one of:

erbium Er, bismuth Bi, ytterbium Yb, thulium Tm.

7. The optical fiber according to any one of claims 1 to 6, wherein the core comprises a first core layer and a second core layer arranged in this order from inside to outside, and the doping concentrations of the rare earth ions are different in the first core layer and the second core layer.

8. The optical fiber of claim 7, wherein the first core layer has a higher doping concentration of the rare earth ions than the second core layer;

In the second core layer, a target dopant is doped, the target dopant being used to raise the refractive index of the second core layer.

9. The optical fiber of claim 8, wherein the radius of the first core layer is r1,2 μm r 14 μm.

10. The optical fiber of claim 7, wherein the second core layer has a higher doping concentration of the rare earth ions than the first core layer;

In the first core layer, a target dopant is doped, the target dopant being used to raise the refractive index of the first core layer.

11. The optical fiber of claim 10, wherein the radius of the first core layer is r2,0 μm r2 μm.

12. An optical communication device comprising the doped fiber of any one of claims 1 to 11 for transmitting an optical signal.

13. An optical communication system, comprising: a pump light source, a communication fiber and a doped fiber, the doped fiber being the fiber of any one of claims 1 to 11;

the communication optical fiber is connected with the doped optical fiber and is used for transmitting signal light;

The pump light source is connected with the doped optical fiber, and pump light emitted by the pump light source is input into the doped optical fiber;

the doped optical fiber is used for absorbing the energy of the pump light and amplifying the signal light.