Erbium-ytterbium co-doped optical fiber, optical fiber amplifier and optical fiber laser
By performing gradient doping in the erbium-ytterbium co-doped fiber core along the length direction and adjusting the proportion of doped components, the problem of low pumping efficiency of existing fibers is solved, and higher pumping efficiency and lower losses are achieved.
Patent Information
- Application Number
- CN202411985653.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-04-11
AI Technical Summary
The existing Erbium-Ytterbium co-doped optical fiber has low pump efficiency and needs further optimization.
By gradient doping along the length of the fiber in the optical fiber core, the molar content of erbium ions doped in the first region is higher than that of the second region, and the molar content of ytterbium ions is also gradiently distributed in different regions, and the core is doped with rare earth ion oxides, alumina, germanium oxide and phosphorus oxide to adjust the molar content of aluminum and rare earth ions.
It improves the pumping efficiency of the optical fiber, enhances the amplification performance and laser performance of the optical fiber, and reduces the loss of the optical fiber.
Smart Images
Figure CN119812904A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of optical fiber amplification, and more specifically, relates to an erbium-ytterbium co-doped optical fiber, an optical fiber amplifier, and an optical fiber laser. Background Art
[0002] With the development of technology, the demand for higher power and wider bandwidth is growing, which promotes the research of new fiber amplifier technology. Erbium-ytterbium co-doped fiber is a special fiber with important applications in optical fiber communication and laser technology. It is made by doping erbium (Er) in the fiber core. 3 +) and ytterbium (Yb 3 +) ions are used to amplify optical signals. The amplification effect of this type of optical fiber mainly depends on the energy level transition of erbium ions, while the co-doping of ytterbium ions helps to improve the utilization efficiency of pump light, because ytterbium ions can sensitize erbium ions and improve the conversion efficiency of energy from pump light source to signal light.
[0003] However, the current erbium-ytterbium co-doped optical fiber still has the problem of insufficient pumping efficiency, which needs further optimization. Summary of the invention
[0004] The invention solves the problem of low pumping efficiency of erbium-ytterbium co-doped optical fiber in the prior art by providing an erbium-ytterbium co-doped optical fiber, an optical fiber amplifier and an optical fiber laser.
[0005] In a first aspect, the present invention provides an erbium-ytterbium co-doped optical fiber, comprising a core, an inner cladding and an outer cladding arranged in sequence from the inside to the outside; the core is divided into a first region and a second region in a direction of increasing optical fiber length, the molar content ratio of erbium ions doped in the first region is higher than the molar content ratio of erbium ions doped in the second region, and the molar content ratio of ytterbium ions doped in the first region is lower than the molar content ratio of ytterbium ions doped in the second region.
[0006] Preferably, the molar content of erbium ions doped into the first region is in the range of 1% to 2%, and the molar content of ytterbium ions doped into the first region is in the range of 1% to 2%; the molar content of erbium ions doped into the second region is in the range of 0.5% to 1%, and the molar content of ytterbium ions doped into the second region is in the range of 2% to 4%.
[0007] Preferably, the molar content ratio of erbium ions in the core satisfies the following distribution function: N1=k1·L+σ1; the molar content ratio of ytterbium ions in the core satisfies the following distribution function: N2=k2·L+σ2; wherein, 0.002<L<0.03; wherein, N1 is the molar content ratio of erbium ions, k1 is the slope of the distribution function corresponding to the molar content ratio of erbium ions, σ1 is the maximum molar content ratio of erbium ions, and L is the length of the optical fiber along the longitudinal direction, in km; N2 is the molar content ratio of ytterbium ions, k2 is the slope of the distribution function corresponding to the molar content ratio of ytterbium ions, and σ2 is the minimum molar content ratio of ytterbium ions.
[0008] Preferably, the fiber core contains rare earth ion oxide, aluminum oxide, germanium oxide and phosphorus oxide, and the rare earth ions are erbium and ytterbium; the molar content ratio of doped aluminum to rare earth ions in the fiber core is between 8:1 and 12:1.
[0009] Preferably, the molar content of germanium oxide is in the range of 2% to 5%, and the molar content of phosphorus oxide is in the range of 15% to 20%.
[0010] Preferably, the fiber core is divided into a fiber core inner layer and a fiber core outer layer along the radial direction; at any length position of the optical fiber along the longitudinal direction, the molar content ratio of erbium ions in the fiber core outer layer at this length position is recorded as a1, and the molar content ratio of ytterbium ions in the fiber core outer layer at this length position is recorded as b1, the molar content ratio of erbium ions in the fiber core inner layer at this length position is 1-a1, and the molar content ratio of ytterbium ions in the fiber core inner layer at this length position is 1-b1; wherein,
[0011] Preferably, the erbium-ytterbium co-doped optical fiber further includes: a coating layer; the relative refractive index difference of the core is in the range of 0.1% to 0.5%, the relative refractive index difference of the inner cladding is in the range of -0.5% to -0.1%, the relative refractive index difference of the outer cladding is 0, and the relative refractive index difference of the coating layer is in the range of -5% to -3%.
[0012] Preferably, the diameter R0 of the fiber core is 8μm to 30μm, the outer contour of the cross section of the inner cladding is a regular polygon, the diameter R1 of the circumscribed circle of the inner cladding is 11μm to 37μm, the diameter R2 of the outer cladding is 125±10μm or 250±10μm, the diameter R3 of the coating layer is 250±15μm or 400±15μm, and R0<R1<R2<R3.
[0013] In a second aspect, the present invention provides a fiber amplifier, wherein the fiber amplifier is a cladding pumped structure, and the optical gain medium of the fiber amplifier adopts the above-mentioned erbium-ytterbium co-doped fiber.
[0014] In a third aspect, the present invention provides a fiber laser, wherein the fiber laser is a cladding pumped structure, and the optical gain medium of the fiber laser adopts the above-mentioned erbium-ytterbium co-doped fiber.
[0015] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:
[0016] (1) The erbium-ytterbium co-doped optical fiber provided by the present invention comprises a core, an inner cladding and an outer cladding arranged in sequence from the inside to the outside, wherein the core is divided into a first region and a second region in sequence along the direction of increasing optical fiber length, the molar content ratio of erbium ions doped in the first region is higher than the molar content ratio of erbium ions doped in the second region, and the molar content ratio of ytterbium ions doped in the first region is lower than the molar content ratio of ytterbium ions doped in the second region. That is, the erbium-ytterbium co-doped optical fiber provided by the present invention is gradient doped along the direction of increasing optical fiber length (longitudinal direction), and different concentrations of doping are achieved in different regions of the core, so that the refractive index distribution and amplification characteristics of the optical fiber can be more accurately controlled, thereby improving the pumping efficiency, obtaining a high-power doped optical fiber, and also helping to improve the balanced gain and noise performance.
[0017] (2) The core of the erbium-ytterbium co-doped optical fiber provided by the present invention contains rare earth ion oxide, aluminum oxide, germanium oxide and phosphorus oxide, the rare earth ions are erbium and ytterbium, wherein the molar content ratio of aluminum doped to rare earth ions in the core is between 8:1 and 12:1. Considering that excessive aluminum in the erbium-ytterbium co-doped optical fiber may be one of the main reasons for the optical fiber output loss after irradiation, and is also prone to the negative impact of increased attenuation, the present invention helps to further improve the energy transfer efficiency and reduce the loss of the optical fiber by adjusting the molar content ratio of aluminum to rare earth ions in the core.
[0018] (3) The molar content of phosphorus oxide in the fiber core of the present invention is in the range of 15% to 20%. The present invention can optimize the energy transfer performance between erbium and ytterbium ions by doping a large amount of phosphorus (P) in the fiber core, thereby greatly suppressing the parasitic fluorescence of ytterbium ions.
[0019] (4) The outer contour of the cross section of the inner cladding in the present invention is designed to be a regular polygon, which can further improve the pumping efficiency.
[0020] (5) The erbium-ytterbium co-doped optical fiber provided by the present invention can further divide the core into radial layers, and the core is divided into an inner core layer and an outer core layer in the radial direction; at any length position of the optical fiber along the longitudinal direction, the molar content ratio of erbium ions in the outer core layer at this length position is recorded as a1, and the molar content ratio of ytterbium ions in the outer core layer at this length position is recorded as b1, the molar content ratio of erbium ions in the inner core layer at this length position is 1-a1, and the molar content ratio of ytterbium ions in the inner core layer at this length position is 1-b1; wherein, The present invention can reduce the background loss of the optical fiber by this radial gradient doping method, and can effectively suppress the concentration quenching phenomenon of erbium ions by reducing the distribution ratio of erbium ions in the outer layer of the fiber core and increasing the distribution ratio of ytterbium ions, thereby optimizing the energy transfer performance between erbium and ytterbium ions, further increasing the energy storage of the fiber core, and improving the amplification performance. The present invention can greatly improve the amplification and laser performance of the optical fiber by combining the longitudinal gradient doping and radial gradient doping methods. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 A schematic diagram showing the change in the molar content ratio of erbium ions and ytterbium ions in the core of an erbium-ytterbium co-doped optical fiber provided by the present invention along the direction of increasing optical fiber length;
[0022] Figure 2 A schematic diagram of the cross-sectional structure of an erbium-ytterbium co-doped optical fiber provided by the present invention;
[0023] Figure 3 A schematic diagram of the layered cross-sectional structure of the core of an erbium-ytterbium co-doped optical fiber provided by the present invention. DETAILED DESCRIPTION
[0024] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0025] In a first aspect, the present invention provides an erbium-ytterbium co-doped optical fiber, see Figures 1 to 3 , comprising a core 100, an inner cladding 200 and an outer cladding 300 arranged in sequence from the inside to the outside; the core 100 is divided into a first region and a second region in the direction of increasing optical fiber length, the molar content of erbium ions doped in the first region is higher than the molar content of erbium ions doped in the second region, and the molar content of ytterbium ions doped in the first region is lower than the molar content of ytterbium ions doped in the second region.
[0026] The molar content of erbium ions doped in the first region is in the range of 1% to 2%, and the molar content of ytterbium ions doped in the first region is in the range of 1% to 2%; the molar content of erbium ions doped in the second region is in the range of 0.5% to 1%, and the molar content of ytterbium ions doped in the second region is in the range of 2% to 4%. That is, the first region is doped with high concentration erbium ions and low concentration ytterbium ions, and the second region is doped with low concentration erbium ions and high concentration ytterbium ions.
[0027] The erbium-ytterbium co-doped optical fiber provided by the present invention is gradient doped, specifically linear doping, that is, the concentration (i.e., molar content ratio) of the two ions (i.e., erbium ions and ytterbium ions) changes with the length as a linear function. For example, the molar content ratio of erbium ions in the fiber core 100 satisfies the following distribution function: N1=k1·L+σ1; the molar content ratio of ytterbium ions in the fiber core 100 satisfies the following distribution function: N2=k2·L+σ2; wherein, 0.002<L<0.03; the preferred value is: 0.002<L<0.03; where N1 is the molar content of erbium ions, k1 is the slope of the distribution function corresponding to the molar content of erbium ions, σ1 is the highest molar content of erbium ions, L is the length of the optical fiber in the longitudinal direction (km), N2 is the molar content of ytterbium ions, k2 is the slope of the distribution function corresponding to the molar content of ytterbium ions, and σ2 is the lowest molar content of ytterbium ions. Gradient doping can improve energy transfer efficiency and slope efficiency (i.e., pump slope efficiency).
[0028] The fiber core 100 is phosphosilicate glass, and the fiber core 100 contains rare earth ion oxide, aluminum oxide, germanium oxide and phosphorus oxide, and the rare earth ions are erbium and ytterbium; the molar content ratio of aluminum doping to rare earth ions in the fiber core 100 is between 8:1 and 12:1. The molar content of germanium oxide is in the range of 2% to 5%, and the molar content of phosphorus oxide is in the range of 15% to 20%. The present invention can reduce the attenuation of the optical fiber by combining high phosphorus doping with reasonable allocation of doping ratio.
[0029] Based on the above solution, the present invention can be further optimized by radially stratifying the fiber core 100. The rare earth ion distribution ratios of different layers of the fiber core are different, and can be specifically adjusted to meet different application requirements.
[0030] Specifically, the fiber core 100 is radially divided into a fiber core inner layer 110 and a fiber core outer layer 120; at any length position of the optical fiber in the longitudinal direction, the molar content ratio of erbium ions in the fiber core outer layer 120 at the length position is recorded as a1, and the molar content ratio of ytterbium ions in the fiber core outer layer 120 at the length position is recorded as b1, the molar content ratio of erbium ions in the fiber core inner layer 110 at the length position is 1-a1, and the molar content ratio of ytterbium ions in the fiber core inner layer 110 at the length position is 1-b1; wherein, The preferred values are:
[0031] The present invention can effectively suppress the concentration quenching phenomenon of erbium ions by reducing the distribution ratio of erbium ions in the outer layer of the fiber core and increasing the distribution ratio of ytterbium ions, and further increase the energy storage of the fiber core to improve the amplification performance. By controlling the two slopes k1 and k2, the concentration of rare earth ions can be accurately controlled along the length of the optical fiber, which is crucial for optimizing the amplification and laser performance of the optical fiber. For example, if k1 is large, it means that the erbium ion concentration changes rapidly with the length, and the erbium ion doping amount can be increased in the inner layer of the fiber core to maintain the performance.
[0032] In addition, the erbium-ytterbium co-doped optical fiber provided by the present invention may also include: a coating layer. The relative refractive index difference of the core 100 is in the range of 0.1% to 0.5%; the relative refractive index difference of the inner cladding 200 is in the range of -0.5% to -0.1%, and the inner cladding 200 is preferably fluorine-doped quartz. The low refractive index quartz cladding can increase the bending resistance of the optical fiber; the relative refractive index difference of the outer cladding 300 is 0, and the outer cladding 300 is preferably pure quartz material, and the relative refractive index difference of the coating layer is in the range of -5% to -3%.
[0033] The diameter R0 of the core 100 is 8 μm to 30 μm, the outer contour of the cross section of the inner cladding 200 is a regular polygon, the diameter R1 of the circumscribed circle of the inner cladding 200 is 11 μm to 37 μm, the diameter R2 of the outer cladding 300 is 125±10 μm or 250±10 μm, the diameter R3 of the coating layer is 250±15 μm or 400±15 μm, and R0<R1<R2<R3.
[0034] The present invention is further described below with reference to a number of examples.
[0035] Embodiment 1:
[0036] Embodiment 1 provides an erbium-ytterbium co-doped optical fiber, comprising a core, an inner cladding and an outer cladding arranged in sequence from the inside to the outside; the diameter R0 of the core is 30 μm, and the relative refractive index difference of the core is 0.3%; the diameter R1 of the circumscribed circle of the inner cladding is 35 μm, and the relative refractive index difference of the inner cladding is -0.2%; the outer cladding is a pure quartz layer, the diameter R2 of the outer cladding is 250 μm, and the relative refractive index difference of the outer cladding is 0; the diameter R3 of the coating is 400 μm, and the relative refractive index difference of the coating is -5%.
[0037] The molar content of erbium ions doped into the first region is 1%, and the molar content of ytterbium ions doped into the first region is 2%; the molar content of erbium ions doped into the second region is 0.5%, and the molar content of ytterbium ions doped into the second region is 3%.
[0038] The slope k1 of the distribution function corresponding to the molar content of erbium ions is The slope k2 of the distribution function corresponding to the molar content of ytterbium ions is
[0039] The ratio of aluminum and rare earth ions doped in the fiber core is 8:1, the molar content of germanium oxide is 2%, and the molar content of phosphorus oxide is 15%.
[0040] The pump slope efficiency of the erbium-ytterbium co-doped optical fiber provided in Example 1 is 30%, and the attenuation is 8 dB.
[0041] Embodiment 2:
[0042] Embodiment 2 provides an erbium-ytterbium co-doped optical fiber, comprising a core, an inner cladding and an outer cladding arranged in sequence from the inside to the outside; the diameter R0 of the core is 15 μm, and the relative refractive index difference of the core is 0.2%; the diameter R1 of the circumscribed circle of the inner cladding is 26 μm, and the relative refractive index difference of the inner cladding is -0.2%; the outer cladding is a pure quartz layer, the diameter R2 of the outer cladding is 125 μm, and the relative refractive index difference of the outer cladding is 0; the diameter R3 of the coating is 250 μm, and the relative refractive index difference of the coating is -5%.
[0043] The molar content of erbium ions doped into the first region is 1.2%, and the molar content of ytterbium ions doped into the first region is 1.5%; the molar content of erbium ions doped into the second region is 0.58%, and the molar content of ytterbium ions doped into the second region is 3%.
[0044] The slope k1 of the distribution function corresponding to the molar content of erbium ions is The slope k2 of the distribution function corresponding to the molar content of ytterbium ions is
[0045] The ratio of aluminum and rare earth ions doped in the fiber core is 10:1, the molar content of germanium oxide is 5%, and the molar content of phosphorus oxide is 15%.
[0046] The pump slope efficiency of the erbium-ytterbium co-doped optical fiber provided in Example 2 is 38%, and the attenuation is 7 dB.
[0047] Embodiment 3:
[0048] Embodiment 3 provides an erbium-ytterbium co-doped optical fiber, comprising a core, an inner cladding and an outer cladding arranged in sequence from the inside to the outside; the diameter R0 of the core is 20 μm, and the relative refractive index difference of the core is 0.2%; the diameter R1 of the circumscribed circle of the inner cladding is 26 μm, and the relative refractive index difference of the inner cladding is -0.2%; the outer cladding is a pure quartz layer, the diameter R2 of the outer cladding is 250 μm, and the relative refractive index difference of the outer cladding is 0; the diameter R3 of the coating is 400 μm, and the relative refractive index difference of the coating is -5%.
[0049] The molar content of erbium ions doped into the first region is 1.12%, and the molar content of ytterbium ions doped into the first region is 2%; the molar content of erbium ions doped into the second region is 0.5%, and the molar content of ytterbium ions doped into the second region is 3.5%.
[0050] The slope k1 of the distribution function corresponding to the molar content of erbium ions is The slope k2 of the distribution function corresponding to the molar content of ytterbium ions is
[0051] The ratio of aluminum and rare earth ions doped in the fiber core is 8:1, the molar content of germanium oxide is 5%, and the molar content of phosphorus oxide is 20%.
[0052] The erbium-ytterbium co-doped optical fiber provided in Example 3 has a pump slope efficiency of 30% and an attenuation of 6 dB.
[0053] Embodiment 4:
[0054] Embodiment 4 provides an erbium-ytterbium co-doped optical fiber, comprising a core, an inner cladding and an outer cladding arranged in sequence from the inside to the outside; the diameter R0 of the core is 25 μm, and the relative refractive index difference of the core is 0.1%; the diameter R1 of the circumscribed circle of the inner cladding is 30 μm, and the relative refractive index difference of the inner cladding is -0.2%; the outer cladding is a pure quartz layer, the diameter R2 of the outer cladding is 250 μm, and the relative refractive index difference of the outer cladding is 0; the diameter R3 of the coating is 400 μm, and the relative refractive index difference of the coating is -5%.
[0055] The molar content of erbium ions doped into the first region is 1.2%, and the molar content of ytterbium ions doped into the first region is 1.5%; the molar content of erbium ions doped into the second region is 0.65%, and the molar content of ytterbium ions doped into the second region is 3%.
[0056] The slope k1 of the distribution function corresponding to the molar content of erbium ions is The slope k2 of the distribution function corresponding to the molar content of ytterbium ions is
[0057] The ratio of aluminum and rare earth ions doped in the fiber core is 12:1, the molar content of germanium oxide is 5%, and the molar content of phosphorus oxide is 20%.
[0058] The pump slope efficiency of the erbium-ytterbium co-doped optical fiber provided in Example 4 is 40%, and the attenuation is 4 dB.
[0059] Embodiment 5:
[0060] Embodiment 5 provides an erbium-ytterbium co-doped optical fiber, comprising a core, an inner cladding and an outer cladding arranged in sequence from the inside to the outside; the diameter R0 of the core is 8 μm, and the relative refractive index difference of the core is 0.2%; the diameter R1 of the circumscribed circle of the inner cladding is 11 μm, and the relative refractive index difference of the inner cladding is -0.2%; the outer cladding is a pure quartz layer, the diameter R2 of the outer cladding is 125 μm, and the relative refractive index difference of the outer cladding is 0; the diameter R3 of the coating is 250 μm, and the relative refractive index difference of the coating is -5%.
[0061] The molar content of erbium ions doped into the first region is 1.2%, and the molar content of ytterbium ions doped into the first region is 1.6%; the molar content of erbium ions doped into the second region is 0.6%, and the molar content of ytterbium ions doped into the second region is 3%.
[0062] The slope k1 of the distribution function corresponding to the molar content of erbium ions is The slope k2 of the distribution function corresponding to the molar content of ytterbium ions is
[0063] The fiber core is also divided into an inner core layer and an outer core layer along the radial direction. The molar content of erbium ions in the outer core layer is a1. The molar content of ytterbium ions in the outer layer of the fiber core is b1.
[0064] The ratio of aluminum and rare earth ions doped in the fiber core is 8:1, the molar content of germanium oxide is 2%, and the molar content of phosphorus oxide is 15%.
[0065] The pump slope efficiency of the erbium-ytterbium co-doped optical fiber provided in Example 5 is 36%, and the attenuation is 5 dB.
[0066] The present invention optimizes the design of the core refractive index profile, doping region, doping concentration and doping components, so that the erbium-ytterbium co-doped optical fiber has higher pump slope efficiency and lower loss.
[0067] In the second and third aspects, the present invention further provides a fiber amplifier and a fiber laser, which are described below in Example 6 and Example 7, respectively.
[0068] Embodiment 6:
[0069] Example 6 provides a fiber amplifier, which is a cladding pumped structure, and the optical gain medium of the fiber amplifier adopts the above-mentioned erbium-ytterbium co-doped fiber (for example, the erbium-ytterbium co-doped fiber described in Examples 1 to 5 can be used).
[0070] The erbium-ytterbium co-doped fiber provided by the present invention is a high-power doped fiber, and the gain effect is compared with the traditional high-power doped fiber, and the pump efficiency is greatly improved. The erbium-ytterbium co-doped fiber provided by the present invention is used as an optical gain medium of a fiber amplifier, and has the advantages of low loss and high gain.
[0071] Embodiment 7:
[0072] Example 7 provides a fiber laser, which is a cladding pumped structure, and the optical gain medium of the fiber laser adopts the above-mentioned erbium-ytterbium co-doped fiber (for example, the erbium-ytterbium co-doped fiber described in Examples 1 to 5 can be used).
[0073] In summary, the present invention achieves higher pumping efficiency and lower loss in erbium-ytterbium co-doped optical fiber by performing regional and layered doping and optimizing the molar ratio and composition of doping, thereby meeting the requirements of modern optical fiber communication systems.
[0074] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.
Claims
1. An erbium-ytterbium co-doped optical fiber, characterized in that: The invention comprises a core, an inner cladding and an outer cladding arranged in sequence from the inside to the outside; the core is divided into a first region and a second region in sequence along the direction of increasing optical fiber length, the molar content ratio of erbium ions doped in the first region is higher than the molar content ratio of erbium ions doped in the second region, and the molar content ratio of ytterbium ions doped in the first region is lower than the molar content ratio of ytterbium ions doped in the second region.
2. The erbium-ytterbium co-doped optical fiber according to claim 1, characterized in that: The molar content of erbium ions doped into the first region is in the range of 1% to 2%, and the molar content of ytterbium ions doped into the first region is in the range of 1% to 2%; the molar content of erbium ions doped into the second region is in the range of 0.5% to 1%, and the molar content of ytterbium ions doped into the second region is in the range of 2% to 4%.
3. The erbium-ytterbium co-doped optical fiber according to claim 2, characterized in that: The molar content ratio of erbium ions in the fiber core satisfies the following distribution function: N1=k1·L+σ1; the molar content ratio of ytterbium ions in the fiber core satisfies the following distribution function: N2=k2·L+σ2; wherein, 0.002<L<0.03; wherein, N1 is the molar content ratio of erbium ions, k1 is the slope of the distribution function corresponding to the molar content ratio of erbium ions, σ1 is the maximum molar content ratio of erbium ions; L is the length of the optical fiber along the longitudinal direction, in km; N2 is the molar content ratio of ytterbium ions, k2 is the slope of the distribution function corresponding to the molar content ratio of ytterbium ions, and σ2 is the minimum molar content ratio of ytterbium ions.
4. The erbium-ytterbium co-doped optical fiber according to claim 2, characterized in that: The fiber core contains rare earth ion oxide, aluminum oxide, germanium oxide and phosphorus oxide, and the rare earth ions are erbium and ytterbium; the molar ratio of doped aluminum to rare earth ions in the fiber core is between 8:1 and 12:
1.
5. The erbium-ytterbium co-doped optical fiber according to claim 4, characterized in that: The molar content of germanium oxide is in the range of 2% to 5%, and the molar content of phosphorus oxide is in the range of 15% to 20%.
6. The Erbium-Ytterbium co-doped optical fiber according to claim 1, characterized in that: The fiber core is divided into a fiber core inner layer and a fiber core outer layer in the radial direction; at any length position of the optical fiber in the longitudinal direction, the molar content ratio of erbium ions in the fiber core outer layer at this length position is recorded as a1, and the molar content ratio of ytterbium ions in the fiber core outer layer at this length position is recorded as b1, the molar content ratio of erbium ions in the fiber core inner layer at this length position is 1-a1, and the molar content ratio of ytterbium ions in the fiber core inner layer at this length position is 1-b1; wherein, 7. The Erbium-Ytterbium co-doped optical fiber according to claim 1, characterized in that: Also includes: coating layer; the relative refractive index difference of the core is in the range of 0.1% to 0.5%, the relative refractive index difference of the inner cladding is in the range of -0.5% to -0.1%, the relative refractive index difference of the outer cladding is 0, and the relative refractive index difference of the coating layer is in the range of -5% to -3%.
8. The Erbium-Ytterbium co-doped optical fiber according to claim 7, characterized in that: The diameter R0 of the fiber core is 8μm to 30μm, the outer contour of the cross section of the inner cladding is a regular polygon, the diameter R1 of the circumscribed circle of the inner cladding is 11μm to 37μm, the diameter R2 of the outer cladding is 125±10μm or 250±10μm, the diameter R3 of the coating layer is 250±15μm or 400±15μm, and R0<R1<R2<R3.
9. An optical fiber amplifier, characterized in that: The optical fiber amplifier is a cladding pumped structure, and the optical gain medium of the optical fiber amplifier adopts the erbium-ytterbium co-doped optical fiber as described in any one of claims 1-8.
10. A fiber laser, characterized in that: The fiber laser is a cladding pumped structure, and the optical gain medium of the fiber laser is the erbium-ytterbium co-doped fiber as claimed in any one of claims 1 to 8.