An extended L-band erbium-doped silicate gain fiber, its preparation method, and its application in fiber amplifiers

Abstract

The present invention relates to an extended L-band (1565nm to 1630+nm) erbium-doped silicate gain fiber, its preparation method, and its application in optical fiber amplifiers. The optical fiber comprises core glass and cladding glass. The core glass comprises selected molar percentages of SiO2, Al2O3, B2O3, Y2O3, MgO, CaO, SrO, BaO, Li2O, Na2O, K2O, and Er2O3. The cladding glass does not contain active rare earth ions (such as Er2O3). 3+ ) and has a lower refractive index than the core glass. This invention uses multi-component silicate glass as the optical fiber gain medium, offering advantages such as high doping concentration, a wide component adjustment range, a wide gain bandwidth, high gain and gain coefficient, and a simple drawing process. The extended L-band gain bandwidth is 70.5 to 101.3 nm, and the half-height cutoff wavelength is 1635.5 to 1666.3 nm.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber preparation, in particular to an extended L-band erbium-doped silicate gain optical fiber, a preparation method thereof, and application in an optical fiber amplifier. Background Art

[0002] The rapid development of the fiber-optic communications industry has led to increased demand for internet transmission capacity and bandwidth, necessitating the development of a new generation of high-capacity fiber-optic communication systems. Erbium-doped fiber is a key component in existing fiber-optic communication systems. Currently, C-band (1530-1565nm) erbium-doped fiber amplifier technology is mature, and L-band (1565-1625nm) erbium-doped fiber amplifiers are the most promising next-generation fiber amplifier products.

[0003] Prior art, Chinese patent CN114180823A discloses a radiation-resistant ultra-wideband L-band erbium-doped fiber, its preparation method, and its application. This technology achieves L-band gain bandwidth enhancement by introducing phosphorus into erbium-doped silica fiber. However, in this approach, the drawing temperature of the silica fiber exceeds 1900°C, which causes severe volatilization of the phosphorus element, ultimately significantly reducing the batch stability and yield of the fiber, greatly increasing the cost and difficulty of practical application of this approach. Therefore, research on erbium-doped glass and optical fibers with large L-band gain bandwidth and high process stability has important scientific significance and application prospects. Summary of the Invention

[0004] The purpose of the present invention is to address the above-mentioned situation and propose an extended L-band erbium-doped silicate gain fiber and its preparation method to solve the above-mentioned problems. The erbium-doped silicate fiber used in the present invention is a multi-component glass fiber with advantages such as a wide composition adjustment range and a high degree of matching between the core glass and the cladding glass. Therefore, it achieves the beneficial effects of a large L-band gain bandwidth and high batch stability. Silicate glass has a high solubility of rare earth ions, which can improve Er 3+ The absorption efficiency of ions to pump light; on the basis of SiO2 as the main glass network structure, Al2O3 and B2O3 are added to improve and optimize the glass network structure and improve the local environment of Er ions; at the same time, this patent adopts Li2O, Na2O, K2O and alkaline earth metals such as MgO, CaO, SrO, BaO and other glass network outer bodies, through component design, using the local ion field strength effect of ions to improve Er 3+ ion Stark splitting is optimized to improve Er 3+ ions in the extended L-band gain bandwidth and flatness. Select the inactive rare earth ion Y 3+ Is used to improve Er 3+ The dispersion of ions in silicate glass avoids clustering, thus achieving Er 3+ High concentration of ions for efficient doping.

[0005] In order to achieve the above object, the technical solution provided by the present invention is:

[0006] An extended L-band erbium-doped silicate gain optical fiber comprises a core glass and a cladding glass. The core glass of the extended L-band erbium-doped silicate optical fiber has the following composition, measured in molar percentage: 40-70 mol% SiO2, 0.1-20 mol% Al2O3, 0.1-20 mol% B2O3, 0.1-5 mol% Y2O3, 0.1-25 mol% MgO, 0.1-25 mol% CaO, 0.1-25 mol% SrO, 0.1-25 mol% BaO, 0.1-30 mol% Li2O, 0.1-30 mol% Na2O, 0.1-30 mol% K2O, and 0.1-3 mol% Er2O3.

[0007] In a preferred embodiment, the core glass component of the extended L-band erbium-doped silicate gain fiber has a content of MgO+CaO greater than 7 mol%, and a content of Li2O+Na2O+K2O greater than 17 mol%.

[0008] The cladding glass does not contain active rare earth ions (such as Er 3+ The core diameter of the optical fiber is 3 to 10 μm, the cladding diameter is 80 to 200 μm, and the numerical aperture (NA) of the core and cladding is 0.07 to 0.26.

[0009] A method for preparing an extended L-band erbium-doped silicate gain fiber comprises the following steps:

[0010] 1) Based on the composition and ratio of the core glass, a silicate core glass is prepared by a melting-quenching method, and the preparation steps are as follows:

[0011] S1: Weigh and mix the raw materials to a composition ratio of 40-70 mol% SiO2, 0.1-20 mol% Al2O3, 0.1-20 mol% B2O3, 0.1-5 mol% Y2O3, 0.1-25 mol% MgO, 0.1-25 mol% CaO, 0.1-25 mol% SrO, 0.1-25 mol% BaO, 0.1-30 mol% Li2O, 0.1-30 mol% Na2O, 0.1-30 mol% K2O, and 0.1-3 mol% Er2O3. MgO, CaO, SrO, BaO, Li2O, Na2O, and K2O are introduced in the form of carbonates. The raw materials are ball milled and mixed in a ball mill for 10 hours at a speed of 50 rpm.

[0012] S2: Glass melting: put the mixed raw materials into a platinum crucible and melt them in a furnace at 1300-1480°C for 1 hour;

[0013] S3: ventilation and dehydration, the molten glass liquid is introduced with oxygen to remove water, the ventilation time is 1 hour;

[0014] S4: clarifying and stirring, clarifying the above glass liquid and stirring it at a temperature of 1350-1520° C. for 2 hours;

[0015] S5: forming and annealing, pouring the clarified glass liquid into a preheated iron mold, and after forming, transferring the glass to an annealing furnace for annealing at a temperature of 500-680° C. for 3 hours, and then cooling to room temperature with the furnace to obtain the silicate core glass.

[0016] 2) Using the tube-and-rod method to insert the core glass into the cladding glass tube to form a preform;

[0017] 3) Drawing the preform into an extended L-band silicate gain fiber.

[0018] Compared with the prior art, the present invention has the following obvious substantial features and significant advantages:

[0019] 1. The use of multi-component silicate glass as the optical fiber gain medium offers advantages such as high doping concentration, wide component adjustment range, wide gain bandwidth, and simple drawing process. The extended L-band gain bandwidth is 70.5 to 101.3 nm, and the half-height cutoff wavelength is 1635.5 to 1666.3 nm.

[0020] 2. Both the core glass and the cladding glass are multi-component glasses, and their softening temperatures and thermal expansion coefficients are highly matched, which effectively solves the problem of volatilization of core components and greatly improves process reliability and yield.

[0021] 3. The present invention has the characteristics of simple structure, low cost and easy industrialization, and has important driving significance for the development of ultra-high-speed, wide-bandwidth and ultra-large-capacity optical fiber communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a fluorescence spectrum of the extended L-band erbium-doped silicate optical fiber core glass in Example 1 of the present invention;

[0023] Figure 2 1585 nm intensity is used as the normalized standard for the fluorescence spectra of the erbium-doped silicate optical fiber core glass in Examples 1 to 8 of the present invention;

[0024] Figure 31585 nm intensity is used as the normalized fluorescence spectrum of the erbium-doped optical fiber core glass in Examples 9 to 13 of the present invention and Comparative Example 1;

[0025] Figure 4 is the ratio of the spontaneous emission intensity at 1625 nm to that at 1585 nm of the erbium-doped optical fiber core glass in Examples 1 to 13 of the present invention and Comparative Example 1 (I 1625 / I 1585 );

[0026] Figure 5 This is a structural diagram of the extended L-band optical fiber amplifier of the present invention;

[0027] Among them, 1 is the L-band seed light, 2 and 10 are isolators, 3 and 9 are wavelength division multiplexers, 4 and 8 are passive quartz fibers, 5 and 7 are fiber fusion points, 6 is the gain fiber to be measured, and 12 and 13 are pump lasers.

[0028] Figure 6 1 is a gain spectrum diagram of Example 12 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0030] Table 1 shows the composition of each embodiment and comparative example, as well as the half-height cut-off wavelength, the half-height width of the extended L band, and the ratio of the spontaneous radiation intensity at 1625 nm to that at 1585 nm (I 1625 / I 1585 ).

[0031] Among them, the extended L band is 1565nm to 1625+nm.

[0032] Normalization to the 1585 nm intensity standard was performed as follows: the fluorescence intensities (linear scale) at all measured wavelengths were divided by the spontaneous emission intensity at 1585 nm.

[0033] The half-height cut-off wavelength was determined by selecting the wavelength in the extended L band at which the fluorescence intensity was half the value at 1585 nm.

[0034] The extended L-band half-width was determined by subtracting 1565 nm from the wavelength of the extended L-band at which the fluorescence intensity is half the value at 1585 nm.

[0035] Table 1: Composition, half-height cut-off wavelength, extended L-band half-height width and spontaneous radiation intensity ratio at 1625nm and 1585nm (I 1625 / I 1585 )

[0036]

[0037] In the practical application of L-band (1565-1625nm) fiber amplifiers, the gain of the fiber output in the L-band depends on the lowest gain point of the fiber in the L-band, and the gain bandwidth depends on the flatness of the L-band gain. Figure 1 The fluorescence spectrum of Er-doped fiber core shows that Er 3+ The fluorescence intensity of the ions begins to decrease from 1565 nm and levels off around 1585 nm. Therefore, in the present invention, the intensity at 1585 nm is used as a normalized standard to compare the gain bandwidth and flatness of the erbium-doped optical fiber in the extended L band in different embodiments and comparative examples.

[0038] Example 1 (see Table 1, Figure 1 、 Figure 2 、 Figure 4 )

[0039] An extended L-band erbium-doped silicate gain fiber comprises core glass and cladding glass. The core glass comprises, by mole percentage, 40 mol% SiO2, 0.1 mol% Al2O3, 20 mol% B2O3, 5 mol% Y2O3, 20 mol% MgO, 0.1 mol% CaO, 0.1 mol% SrO, 0.1 mol% BaO, 0.1 mol% Li2O, 0.1 mol% Na2O, 13.4 mol% K2O, and 1 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1300°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1350°C), forming, and annealing (annealing temperature: 500°C). The core glass is processed into a glass sheet with a thickness of 1mm, which is pumped by a pump laser (usually 980nm), and the emitted light in the range of 1400-1700nm is collected by a spectrum analyzer. Secondly, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 3μm, a cladding diameter of 80μm, a numerical aperture of 0.22, and a refractive index difference of 1.1% between the core and cladding. The fluorescence spectrum of the fiber core glass is as follows: Figure 1 The normalized emission spectrum of the fiber core glass at 1585 nm is shown as Figure 2The half-height cutoff wavelength of this fiber is 1652nm, the half-height width of the extended L band is 87nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.87, as shown in Figure 4 shown.

[0040] Example 2 (see Table 1, Figure 2 、 Figure 4 )

[0041] An extended L-band erbium-doped silicate gain fiber comprises core glass and cladding glass. The core glass comprises, by mole percentage, 45.2 mol% SiO2, 2.1 mol% Al2O3, 10 mol% B2O3, 0.1 mol% Y2O3, 0.1 mol% MgO, 4.6 mol% CaO, 25 mol% SrO, 7.2 mol% BaO, 0.5 mol% Li2O, 5 mol% Na2O, 0.1 mol% K2O, and 0.1 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass (melting temperature: 1348°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1390°C), forming, and annealing (annealing temperature: 550°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Next, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 3.5 μm, a cladding diameter of 120 μm, a numerical aperture of 0.07, and a core-cladding refractive index difference of 0.1%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown in Figure 2. Figure 2 The half-height cutoff wavelength of this optical fiber is 1644.3nm, the half-height width of the extended L band is 79.3nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.78, as shown in Figure 4 shown.

[0042] Example 3 (see Table 1, Figure 2 、 Figure 4 )

[0043] An extended L-band erbium-doped silicate gain fiber comprises core glass and cladding glass. The core glass comprises, by mole percentage, 47.1 mol% SiO2, 5 mol% Al2O3, 3.1 mol% B2O3, 1.5 mol% Y2O3, 0.5 mol% MgO, 1.8 mol% CaO, 4.3 mol% SrO, 4.6 mol% BaO, 30 mol% Li2O, 0.4 mol% Na2O, 0.3 mol% K2O, and 1.4 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1310°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1341°C), forming, and annealing (annealing temperature: 520°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Next, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 4 μm, a cladding diameter of 130 μm, a numerical aperture of 0.19, and a core-cladding refractive index difference of 0.8%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown in Figure 2. Figure 2 The half-height cutoff wavelength of this fiber is 1642nm, the half-height width of the extended L band is 77nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.74, as shown in Figure 4 shown.

[0044] Example 4 (see Table 1, Figure 2 、 Figure 4 )

[0045] An extended L-band erbium-doped silicate gain fiber comprises a core glass and a cladding glass. The core glass comprises, by mole percentage, 48.2 mol% SiO2, 20 mol% Al2O3, 0.5 mol% B2O3, 0.4 mol% Y2O3, 0.4 mol% MgO, 0.2 mol% CaO, 1.9 mol% SrO, 25 mol% BaO, 0.1 mol% Li2O, 0.1 mol% Na2O, 0.2 mol% K2O, and 3.0 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1410°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1445°C), forming, and annealing (annealing temperature: 590°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Next, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 3.1 μm, a cladding diameter of 110 μm, a numerical aperture of 0.26, and a core-cladding refractive index difference of 3%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown in Figure 2. Figure 2 The half-height cutoff wavelength of this fiber is 1642nm, the half-height width of the extended L band is 77nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.75, as shown in Figure 4 shown.

[0046] Example 5 (see Table 1, Figure 2 、 Figure 4 )

[0047] An extended L-band erbium-doped silicate gain fiber comprises a core glass and a cladding glass. The core glass comprises, by mole percentage, 54 mol% SiO2, 6 mol% Al2O3, 0.1 mol% B2O3, 0.1 mol% Y2O3, 4.0 mol% MgO, 25 mol% CaO, 4.1 mol% SrO, 3.2 mol% BaO, 2.1 mol% Li2O, 0.7 mol% Na2O, 0.1 mol% K2O, and 0.6 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1450°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1475°C), forming, and annealing (annealing temperature: 630°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Next, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 6 μm, a cladding diameter of 130 μm, a numerical aperture of 0.16, and a core-cladding refractive index difference of 0.6%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown in Figure 2. Figure 2 The half-height cutoff wavelength of this fiber is 1638nm, the half-height width of the extended L band is 73nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.69, as shown in Figure 4 shown.

[0048] Example 6 (see Table 1, Figure 2 、 Figure 4 )

[0049] An extended L-band erbium-doped silicate gain fiber comprises a core glass and a cladding glass. The core glass comprises, by mole percentage, 58 mol% SiO2, 3.5 mol% Al2O3, 2.8 mol% B2O3, 1.2 mol% Y2O3, 10.0 mol% MgO, 15.0 mol% CaO, 1.5 mol% SrO, 3.8 mol% BaO, 1.2 mol% Li2O, 1.2 mol% Na2O, 1.3 mol% K2O, and 0.5 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1435°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1465°C), forming, and annealing (annealing temperature: 620°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Next, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 6 μm, a cladding diameter of 125 μm, a numerical aperture of 0.15, and a core-cladding refractive index difference of 0.5%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown in Figure 2. Figure 2 The half-height cutoff wavelength of this optical fiber is 1637.5nm, the half-height width of the extended L band is 72.5nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.68, as shown in Figure 4 shown.

[0050] Example 7 (see Table 1, Figure 2 、 Figure 4 )

[0051] An extended L-band erbium-doped silicate gain fiber comprises a core glass and a cladding glass. The core glass comprises, by mole percentage, 57.1 mol% SiO2, 5.5 mol% Al2O3, 4.5 mol% B2O3, 0.3 mol% Y2O3, 25.0 mol% MgO, 3.8 mol% CaO, 1.5 mol% SrO, 1.2 mol% BaO, 0.4 mol% Li2O, 0.2 mol% Na2O, 0.1 mol% K2O, and 0.4 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1480°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1520°C), forming, and annealing (annealing temperature: 680°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Secondly, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform rod; finally, the preform rod is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 5.5 μm, a cladding diameter of 128 μm, a numerical aperture of 0.14, and a core-cladding refractive index difference of 0.45%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown as follows: Figure 2 The half-height cutoff wavelength of this optical fiber is 1636.0nm, the half-height width of the extended L band is 71.0nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.68, as shown in Figure 4 shown.

[0052] Example 8 (see Table 1, Figure 2 、 Figure 4 )

[0053] An extended L-band erbium-doped silicate gain fiber comprises a core glass and a cladding glass. The core glass comprises, by mole percentage, 55.0 mol% SiO2, 4.9 mol% Al2O3, 0.6 mol% B2O3, 0.2 mol% Y2O3, 15.0 mol% MgO, 0.3 mol% CaO, 0.2 mol% SrO, 0.3 mol% BaO, 1.2 mol% Li2O, 15.1 mol% Na2O, 6.7 mol% K2O, and 0.5 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1440°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1470°C), forming, and annealing (annealing temperature: 640°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Next, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 5.8 μm, a cladding diameter of 129 μm, a numerical aperture of 0.15, and a core-cladding refractive index difference of 0.51%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown in Figure 2. Figure 2 The half-height cutoff wavelength of this optical fiber is 1635.5nm, the half-height width of the extended L band is 70.5nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.67, as shown in Figure 4 shown.

[0054] Example 9 (see Table 1, Figure 3 、 Figure 4 )

[0055] An extended L-band erbium-doped silicate gain fiber comprises a core glass and a cladding glass. The core glass comprises, by mole percentage, 55.0 mol% SiO2, 2.5 mol% Al2O3, 0.8 mol% B2O3, 0.1 mol% Y2O3, 5.0 mol% MgO, 3.5 mol% CaO, 1.37 mol% SrO, 0.2 mol% BaO, 0.3 mol% Li2O, 30.0 mol% Na2O, 0.75 mol% K2O, and 0.48 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1420°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1450°C), forming, and annealing (annealing temperature: 610°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Secondly, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 6.1 μm, a cladding diameter of 200 μm, a numerical aperture of 0.15, and a core-cladding refractive index difference of 0.48%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown as follows: Figure 3 The half-height cutoff wavelength of this optical fiber is 1666.3nm, the half-height width of the extended L band is 101.3nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 1.42, as shown in Figure 4 shown.

[0056] Example 10 (see Table 1, Figure 3 、 Figure 4 )

[0057] An extended L-band erbium-doped silicate gain fiber comprises a core glass and a cladding glass. The core glass comprises, by mole percentage, 49.8 mol% SiO2, 1.8 mol% Al2O3, 0.5 mol% B2O3, 0.7 mol% Y2O3, 6.0 mol% MgO, 1.3 mol% CaO, 0.8 mol% SrO, 4.0 mol% BaO, 1.2 mol% Li2O, 3.5 mol% Na2O, 30.0 mol% K2O, and 0.4 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1430°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1460°C), forming, and annealing (annealing temperature: 625°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Next, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 5.7 μm, a cladding diameter of 122 μm, a numerical aperture of 0.16, and a core-cladding refractive index difference of 0.55%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown in Figure 2. Figure 3 The half-height cutoff wavelength of this optical fiber is 1666.1nm, the half-height width of the extended L band is 101.1nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 1.27, as shown in Figure 4 shown.

[0058] Example 11 (see Table 1, Figure 3 、 Figure 4 )

[0059] An extended L-band erbium-doped silicate gain fiber comprises a core glass and a cladding glass. The core glass comprises, by mole percentage, 70.0 mol% SiO2, 0.6 mol% Al2O3, 0.4 mol% B2O3, 0.1 mol% Y2O3, 4.1 mol% MgO, 3.2 mol% CaO, 0.4 mol% SrO, 3.6 mol% BaO, 0.1 mol% Li2O, 15.0 mol% Na2O, 2.0 mol% K2O, and 0.5 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1430°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1460°C), forming, and annealing (annealing temperature: 625°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Next, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 5.8 μm, a cladding diameter of 150 μm, a numerical aperture of 0.15, and a core-cladding refractive index difference of 0.51%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown in Figure 2. Figure 3 The half-height cutoff wavelength of this optical fiber is 1663.5nm, the half-height width of the extended L band is 98.5nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 1.19, as shown in Figure 4 shown.

[0060] Example 12 (see Table 1, Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 )

[0061] An extended L-band erbium-doped silicate gain fiber comprises a core glass and a cladding glass. The core glass comprises, by mole percentage, 54.2 mol% SiO2, 1.8 mol% Al2O3, 0.7 mol% B2O3, 0.6 mol% Y2O3, 20.2 mol% MgO, 1.3 mol% CaO, 0.1 mol% SrO, 0.8 mol% BaO, 0.7 mol% Li2O, 9.1 mol% Na2O, 10.0 mol% K2O, and 0.5 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass (melting temperature: 1460°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1530°C), forming, and annealing (annealing temperature: 675°C). The core glass is processed into a glass sheet with a thickness of 1 mm, which is pumped by a pump laser (usually 980 nm), and the emitted light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. Next, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform. Finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 5.7 μm, a cladding diameter of 130 μm, a numerical aperture of 0.18, and a core-cladding refractive index difference of 0.68%. The normalized emission spectrum of the fiber core glass at 1585 nm is shown in Figure 2. Figure 3 The half-height cutoff wavelength of this optical fiber is 1655.0nm, the half-height width of the extended L band is 90.0nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.96, as shown in Figure 4 shown.

[0062] According to the national standard GB / T 18898.2-2008, the gain of the optical fiber in the L band is tested. The test system structure diagram is as follows: Figure 5 As shown, a 976nm laser is used as the pump source. The pump powers of LD1 and LD2 are 650mW and 660mW respectively. The length of the erbium-doped silicate fiber used is 1.5m. The absorption coefficient of the fiber at 976nm is 124dB / m. The gain spectrum of the fiber in the L band is as shown in FIG. Figure 6 As shown, the gain at a wavelength of 1625 nm is 10.7 dB, and the gain coefficient per unit length is 7.1 dB / m@1625 nm.

[0063] Example 13 (see Table 1, Figure 3 、 Figure 4 )

[0064] An extended L-band erbium-doped silicate gain fiber comprises a core glass and a cladding glass. The core glass comprises, by mole percentage, 62.5 mol% SiO2, 2.8 mol% Al2O3, 1.8 mol% B2O3, 0.5 mol% Y2O3, 10.0 mol% MgO, 3.1 mol% CaO, 2.3 mol% SrO, 3.1 mol% BaO, 1.2 mol% Li2O, 4.2 mol% Na2O, 8.0 mol% K2O, and 0.5 mol% Er2O3. The cladding glass is commercial borosilicate glass. The silicate core glass is first prepared using a melt-quench method. The preparation steps include weighing the raw materials, mixing the powders, melting the glass liquid (melting temperature: 1440°C), aerating and removing water, clarifying and stirring (clarifying temperature: 1470°C), forming, and annealing (annealing temperature: 651°C). The core glass is processed into a glass sheet with a thickness of 1mm, pumped by a pump laser (usually 980nm), and the emitted light in the range of 1400-1700nm is collected by a spectrum analyzer. Secondly, the core glass is processed into a glass rod, which is inserted into a cladding glass tube to form a preform; finally, the preform is drawn into an extended L-band erbium-doped silicate gain fiber with a core diameter of 5.5μm, a cladding diameter of 140μm, and a numerical aperture of 0.19. The normalized emission spectrum of the fiber core glass at 1585nm is shown as follows: Figure 3 The half-height cutoff wavelength of this optical fiber is 1642.0nm, the half-height width of the extended L band is 77.0nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.76, as shown in Figure 4 shown.

[0065] Comparative Example 1 (see Table 1, Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 )

[0066] To compare the technical effects of the present invention, a high-phosphorus-doped erbium quartz fiber was selected as a comparative example. The core composition of this quartz fiber was 91.9 mol% SiO2, 8.0 mol% P2O5, and 0.1 mol% Er2O3. The preparation method of this quartz fiber is as follows: 1) Depositing a loose layer. A loose layer was deposited on the inner wall of a quartz glass tube using a modified chemical vapor deposition method; 2) Immersing and doping. The quartz glass tube was immersed in a 0.005 mol / L ErCl3 solution for 3 hours, and the solution was then poured out; 3) Drying. The immersed quartz glass tube was dried by passing nitrogen gas, and then dried by passing chlorine gas; 4) Phosphorus doping. Phosphorus doping was performed by passing POCl3 at a temperature of 1250°C; 5) Preform preparation. The quartz glass tube was vitrified and sintered into a transparent preform. The preform is sliced into glass sheets with a thickness of 1 mm, pumped by a pump laser (usually 980 nm), and the emission light in the range of 1400 to 1700 nm is collected by a spectrum analyzer. 5) The preform is drawn into a quartz optical fiber. The core diameter of the quartz optical fiber is 5 μm, the cladding diameter is 125 μm, and the normalized emission spectrum of the fiber core glass at 1585 nm is as follows: Figure 3 The half-height cutoff wavelength of this optical fiber is 1616.0nm, the half-height width of the extended L band is 51.0nm, and the ratio of the intensity at 1625nm to the intensity at 1585nm is 0.24, as shown in Figure 4 shown.

[0067] According to the national standard GB / T 18898.2-2008, the gain of the optical fiber in the L band is tested. The test system structure diagram is as follows: Figure 5 As shown, a 976nm laser is used as the pump source. The pump powers of LD1 and LD2 are 650mW and 660mW respectively. The length of the erbium-doped silicate fiber used is 15.5m. The absorption coefficient of the fiber at 976nm is 12.1dB / m. The gain spectrum of the fiber in the L band is as shown in FIG. Figure 6 As shown, the gain at a wavelength of 1625 nm is 6.8 dB, and the gain coefficient per unit length is 0.44 dB / m@1625 nm.

[0068] In order to better understand the content of the present invention, it is explained here that based on the characteristics of the erbium ion gain spectrum, the gain performance of the erbium-doped fiber in the L band depends on the gain minimum point, that is, the gain value at 1625nm. Figure 6 It can be seen that the gain (10.7 dB @ 1625 nm) and gain coefficient (7.1 dB / m @ 1625 nm) of the erbium-doped silica fiber of the present invention in the L band are both higher than those of the high-phosphorus-doped erbium-doped silica fiber (6.8 dB, 0.44 dB / m @ 1625 nm).

[0069] Table 1 shows that compared with Examples 1 to 8, Examples 9 to 12 simultaneously meet the characteristics of the core glass components MgO + CaO content greater than 7 mol%, and the content of Li2O + Na2O + K2O greater than 17 mol%, and ultimately achieve the beneficial effect of significantly improving the half-height cutoff wavelength and the half-height width of the extended L band ( Figure 4 ), reflecting the beneficial technical effect of the present invention of improving the L-band gain bandwidth by adjusting the local field strength of erbium ions by the content of alkali metals and alkaline earth metals.

[0070] Figures 2 to 6 The results show that compared to high-phosphorus-doped erbium silicate fiber, the extended L-band erbium-doped silica fiber of the present invention exhibits advantageous technical benefits such as a wide extended L-band gain range, high gain bandwidth, and high gain coefficient. Specifically, compared to the 51.0 nm gain bandwidth, 1616 nm half-height cutoff wavelength, and 0.44 dB / m @ 1625 nm gain coefficient of high-phosphorus-doped erbium silicate fiber, the erbium-doped silica fiber of the present invention exhibits a larger extended L-band gain bandwidth of 70.5 to 101.3 nm, a higher half-height cutoff wavelength of 1635.5 to 1666.3 nm, and a higher gain coefficient of 7.1 dB / m @ 1625 nm. This invention provides an erbium-doped gain fiber for L-band fiber amplifiers with a wide gain bandwidth, high gain and gain coefficient, and high gain flatness.

[0071] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. An extended L-band erbium-doped silicate gain fiber, comprising core glass and cladding glass, characterized in that: The core glass has a composition, in molar percentages, of 40-70 mol% SiO2, 0.1-20 mol% Al2O3, 0.1-20 mol% B2O3, 0.1-5 mol% Y2O3, 0.1-25 mol% MgO, 0.1-25 mol% CaO, 0.1-25 mol% SrO, 0.1-25 mol% BaO, 0.1-30 mol% Li2O, 0.1-30 mol% Na2O, 0.1-30 mol% K2O, and 0.1-3 mol% Er2O3, with the SrO+Li2O content being 0.2-34.3 mol%.

2. The extended L-band erbium-doped silicate gain fiber according to claim 1, characterized in that: The content of the core glass components MgO+CaO is greater than 7 mol %, and the content of Li 2 O+Na 2 O+K 2 O is greater than 17 mol %.

3. The extended L-band erbium-doped silicate gain fiber according to claim 1, wherein: The core glass composition is 55.0mol% SiO2, 2.5mol% Al2O3, 0.8mol% B2O3, 0.1mol% Y2O3, 5.0mol% MgO, 3.5mol% CaO, 1.37mol% SrO, 0.2mol% BaO, 0.3mol% Li2O, 30.0mol% Na2O, 0.75mol% K2O, and 0.48mol% Er2O3.

4. The extended L-band erbium-doped silicate gain fiber according to claim 1, wherein: The core glass composition is 54.2mol% SiO2, 1.8mol% Al2O3, 0.7mol% B2O3, 0.6mol% Y2O3, 20.2mol% MgO, 1.3mol% CaO, 0.1mol% SrO, 0.8mol% BaO, 0.7mol% Li2O, 9.1mol% Na2O, 10.0mol% K2O, and 0.5mol% Er2O3.

5. The extended L-band erbium-doped silicate gain fiber according to claim 1, wherein: The Na2O content of the core glass component is 9-20 mol%.

6. The extended L-band erbium-doped silicate gain fiber according to claim 1, characterized in that: The cladding glass does not contain active rare earth ions and has a lower refractive index than the core glass. The core diameter of the optical fiber is 3-10 μm, the cladding diameter is 80-200 μm, and the numerical aperture between the core glass and the cladding glass is 0.07-0.

26.

7. A method for preparing an extended L-band erbium-doped silicate gain fiber, characterized in that: Here are the steps: 1) The core glass composition, in molar percentages, is as follows: 40~70mol% SiO2, 0.1~20mol% Al2O3, 0.1~20mol% B2O3, 0.1~5mol% Y2O3, 0.1~25mol% MgO, 0.1~25mol% CaO, 0.1~25mol% SrO, 0.1~25mol% BaO, 0.1~30mol% Li2O, 0.1~30mol% Na2O, 0.1~30mol% K2O, 0.1~3mol% Er2O3, and SrO+ The content of Li2O is 0.2-34.3 mol%, and the silicate core glass is prepared by a melt-quenching method, the preparation steps comprising: weighing raw materials, mixing powders, melting glass liquid at a melting temperature of 1300-1480°C, aeration and dehydration, clarification and stirring at a clarification temperature of 1350-1520°C, forming and annealing at a temperature of 500-680°C; 2) Use the tube-rod method to insert the core glass into the cladding glass tube to form a preform; 3) Drawing the preform into an extended L-band silicate gain fiber.

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