CN112390524A - Optical fiber preform preparation method, optical fiber preparation method and optical fiber - Google Patents
Optical fiber preform preparation method, optical fiber preparation method and optical fiber Download PDFInfo
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- CN112390524A CN112390524A CN202011289046.1A CN202011289046A CN112390524A CN 112390524 A CN112390524 A CN 112390524A CN 202011289046 A CN202011289046 A CN 202011289046A CN 112390524 A CN112390524 A CN 112390524A
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- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
- C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
- C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
- C03B37/01853—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
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Abstract
The invention discloses a preparation method of an optical fiber preform, which comprises the following steps: doping phosphorus on the inner wall of the base pipe; doping ytterbium on the inner wall of the base pipe; the substrate tube is fused into an optical fiber preform. The invention also discloses an optical fiber preparation method, which comprises the optical fiber preform preparation method and further comprises the following steps: the optical fiber preform is drawn into an optical fiber. The phosphorus and ytterbium are doped in the process of manufacturing the optical fiber, so that the concave or fluctuation of the central refractive index of the fiber core of the large-mode-field ytterbium-doped optical fiber is reduced or eliminated, and the stability and the gain efficiency of the large-mode-field laser are improved.
Description
Technical Field
The invention relates to the field of new material inorganic nonmetallic materials, in particular to a preparation method of an optical fiber preform, a preparation method of an optical fiber and the optical fiber.
Background
Fiber lasers typically consist of a pump source, a gain fiber, and a resonant cavity. The gain fiber is typically a rare earth doped glass fiber, which is the core of a fiber laser. The pumping source provides energy to enable rare earth ions in the gain fiber to generate spontaneous radiation and stimulated radiation; the resonant cavity realizes the back-and-forth oscillation of signal light and finally realizes laser output. Compared with a gas laser and a traditional solid laser, the optical fiber laser is formed by welding or connecting a gain optical fiber and an optical fiber device (such as an optical fiber grating, an optical fiber coupler, an optical fiber polarization controller and the like), and has the advantages of compact structure, high beam quality, good heat dissipation, high stability, easiness in adjusting output wavelength and the like, so that the optical fiber laser is widely applied to military and civil fields such as optical fiber communication, biomedical treatment, material processing, atmosphere monitoring, laser radar and the like. With the development of science and technology and the demand of society, many application fields require the light source to realize high-power, stable, high-efficiency and tunable laser output in a wider wavelength range, so that ultra-wideband, tunable, high-power and ultra-compact fiber lasers become research hotspots.
As the energy of fiber lasers has gradually increased, the conventional methods and structures for manufacturing communication fibers have been unable to meet the requirements of high beam quality and high power fiber lasers for optical fibers. In order to achieve high beam quality laser output and possibly overcome the limitations of both cross-sectional laser damage and nonlinear effects on power enhancement, the fiber should be designed and selected with a minimum doped core Numerical Aperture (NA) and a corresponding increase in core diameter, so that the mode field diameter of the fundamental transverse mode LP01 is increased, and this technique of achieving a large core diameter fiber by decreasing NA is called large mode field area fiber (LMAF) technique.
The large mode field ytterbium-doped optical fiber on the market at present is usually prepared by a base tube by using MCVD (modified chemical vapor deposition) and a solution doping method, but the uniform distribution of the refractive index and rare earth ions is difficult to obtain. From the earlier reported literature, there is a deep index dip or undulation in the center of the core of large mode field ytterbium-doped fiber (as shown in FIG. 1), which is caused by material volatilization during the sintering process. Fluctuation of the refractive index of the core region also affects the stability of large mode field laser, which is not favorable for obtaining stable laser output with diffraction limit.
Disclosure of Invention
The invention provides an optical fiber preform preparation method, an optical fiber preparation method and an optical fiber, which can reduce or eliminate the central refractive index depression or fluctuation of the fiber core of the large mode field ytterbium-doped optical fiber and improve the stability and gain efficiency of large mode field laser.
A method for preparing an optical fiber preform, comprising the steps of:
doping phosphorus on the inner wall of the base pipe;
doping ytterbium on the inner wall of the base pipe;
fusing the base tube into an optical fiber perform;
preferably, the step of "doping the inner wall of the base pipe with phosphorus" specifically comprises the following steps: the method comprises the steps of enabling chloride to enter the interior of a base pipe from one end of the base pipe through oxygen, heating the interior of the base pipe, heating the chloride in the base pipe to react to generate a glass body, and depositing the glass body on the inner wall of the base pipe.
Preferably, the chlorides include phosphorus oxychloride, silicon tetrachloride and germanium tetrachloride.
Preferably, the step of "doping ytterbium in the inner wall of the base pipe" specifically comprises the steps of: the vitreous body of the inner wall of the substrate tube is soaked by using a solution containing ytterbium salt.
Preferably, the inner wall of the substrate tube is polished prior to the step of "doping the inner wall of the substrate tube with phosphorus".
Preferably, the step of "polishing the inner wall of the substrate tube" specifically comprises the steps of: using SF6And oxygen is introduced into the interior of the substrate tube and the substrate tube is moved using a heating source.
Preferably, the temperature of the heating source is 1850-2200 ℃.
Preferably, the step of collapsing the substrate tube into the optical fiber preform specifically comprises the steps of: the base tube after being doped with ytterbium is installed on the improved chemical vapor deposition equipment and is fused into the optical fiber prefabricated rod at 2000-2300 deg.c.
A preparation method of an optical fiber comprises the preparation method of the optical fiber preform and further comprises the following steps: the optical fiber preform is drawn into an optical fiber.
An optical fiber is obtained by the optical fiber preparation method.
The invention has the beneficial effects that: by doping with phosphorus and ytterbium during the manufacture of the fiber. Thereby reducing or eliminating the concave or fluctuation of the central refractive index of the fiber core of the large mode field ytterbium-doped fiber and improving the stability and gain efficiency of the large mode field laser.
Drawings
FIG. 1 is a schematic representation of the refractive index of the core of a conventional large mode field ytterbium-doped fiber;
FIG. 2 is a schematic illustration of the steps of a method for making an optical fiber;
FIG. 3 is a schematic view of the radial refractive index profile of an optical fiber that is not doped with phosphorus;
FIG. 4 is a schematic view of the radial refractive index profile of a phosphor-doped optical fiber; and
FIG. 5 is a schematic structural diagram of a large mode field ytterbium-doped fiber.
Wherein, 1-fiber core, 2-inner cladding, 3-outer cladding and 4-protective layer.
Detailed Description
The embodiment of the invention provides an optical fiber preform preparation method and an optical fiber preparation method, so that the depression or fluctuation of the central refractive index of the fiber core of the large-mode-field ytterbium-doped optical fiber is reduced or eliminated, and the stability and the gain efficiency of large-mode-field laser are improved.
The first embodiment is as follows:
as shown in fig. 2, a method for fabricating an optical fiber preform includes the steps of:
and S100, doping phosphorus into the inner wall of the base pipe. In the process of doping phosphorus on the inner wall of the base tube, chloride enters the base tube from one end of the base tube by using oxygen or helium, the chloride is heated and reacts to generate loose glass body outside the base tube, and the glass body is deposited on the inner wall of the base tube. Chlorides include phosphorus oxychloride, silicon tetrachloride and germanium tetrachloride, wherein phosphorus oxychloride can also be replaced with other phosphorus compounds. The glass body after reaction contains phosphorus element, so that the inner wall of the base tube can achieve the effect of phosphorus doping. The chemical formula of the reaction of heating and reacting the chloride to generate the glass body is as follows:
SiCl4+O2＝SiO2+2Cl2↑
GeCl4+O2＝GeO2+2Cl2↑
4POCl3+3O2＝2P2O5+6Cll2↑
and step S120, doping ytterbium on the inner wall of the base pipe. In the process of doping ytterbium on the inner wall of the base pipe, the loose glass body on the inner wall of the base pipe is soaked by using a solution containing ytterbium salt, or by using a solution containing ytterbium and containing aluminum salt. The soaking time is 15-60 minutes, wherein the effect is optimal in 15 minutes, 30 minutes or 60 minutes. In other embodiments, soaking with erbium-containing salt solution is also possible.
Step S140, fusing the base tube into an optical fiber prefabricated rod. In the process of fusing and shrinking the base tube into the optical fiber preform, the base tube doped with ytterbium is arranged on MCVD equipment, and the base tube is fused and shrunk into the optical fiber preform by high temperature, wherein the temperature range is 2000-2300 ℃, 2000 ℃, 2100 ℃ or 2300 ℃ and the effect is optimal.
The melting speed range of melting and shrinking the substrate tube into the optical fiber preform is 0.5mm/min-9 mm/min. Wherein the melt shrinkage speed can be 0.5mm/min, 2mm/min, 5mm/min or 9 mm/min. The loose glass body forms the rod core of the optical fiber preform rod in the preform rod manufacturing process, and the rod core forms the fiber core 1 of the optical fiber in the drawing process.
After the preform not doped with phosphorus is drawn into an optical fiber, the refractive index distribution of the fiber core measured by using an optical fiber radial refractive index distribution measuring instrument is shown in fig. 3, and fig. 3 is a schematic view of the refractive index distribution of the optical fiber not doped with phosphorus, wherein the abscissa of fig. 3 is the radial position of the cross section of the optical fiber, and the ordinate is the measured refractive index data.
After the preform doped with phosphorus is drawn into an optical fiber, the refractive index profile of the core is measured by using an optical fiber radial refractive index profile measuring instrument, and the refractive index profile is shown in fig. 4, where fig. 4 is a schematic view of the refractive index profile of the phosphorus-doped optical fiber in the radial direction. Wherein the abscissa of fig. 4 is the radial position of the cross-section of the optical fiber and the ordinate is the measured refractive index data. Comparing the experimental data of fig. 3 and 4, it is found that the central refractive index depression of the core of the large mode field ytterbium-doped fiber is reduced by doping phosphorus, and the stability and gain efficiency of the large mode field laser are improved.
The phosphorus-doped large-mode-field ytterbium-doped fiber is used for research and development of a fiber laser, and long-time practical application shows that compared with a phosphorus-undoped large-mode-field ytterbium-doped fiber, the background loss is reduced to some extent, and the photon darkening effect of the large-mode-field ytterbium-doped fiber is reduced.
Example two:
a method for preparing an optical fiber preform, comprising the steps of:
step S100, polishing the inner wall of the base tube. During the polishing of the inner wall of the substrate tube, SF6 (sulfur hexafluoride) and oxygen were introduced into the interior of the substrate tube and the substrate tube was moved using a heating source. The chemical reaction of SF6 (sulfur hexafluoride) and oxygen inside the substrate tube generates HF (hydrogen fluoride), which is used for corroding the inner wall of the substrate tube to achieve the polishing effect of the inner wall of the substrate tube. Helium can be added into SF6 (sulfur hexafluoride) and oxygen to be input into the base tube, and the base tube is moved by using a heating source, so that the polishing effect of the inner wall of the base tube is achieved, and the inner wall of the base tube is favorably doped with phosphorus. Chlorine can also be added into the sulfur hexafluoride, and the chlorine can dry the inner wall of the base pipe to remove water molecules in the base pipe. Wherein the heating temperature is 1850-.
And step S110, doping phosphorus on the inner wall of the base pipe. In the process of doping phosphorus on the inner wall of the base tube, chloride enters the base tube from one end of the base tube by using oxygen or helium, the chloride is heated and reacts to generate loose glass body outside the base tube, and the glass body is deposited on the inner wall of the base tube. Chlorides include phosphorus oxychloride, silicon tetrachloride and germanium tetrachloride, wherein phosphorus oxychloride can also be replaced with other phosphorus compounds. The glass body after reaction contains phosphorus element, so that the inner wall of the base tube can achieve the effect of phosphorus doping. The chemical formula of the reaction of heating and reacting the chloride to generate the glass body is as follows:
SiCl4+O2＝SiO2+2Cl2↑
GeCl4+O2＝GeO2+2Cl2↑
4POCl3+3O2＝2P2O5+6Cll2↑
and step S120, doping ytterbium on the inner wall of the base pipe. In the process of doping ytterbium on the inner wall of the base pipe, the loose glass body on the inner wall of the base pipe is soaked by using a solution containing ytterbium salt, or by using a solution containing ytterbium and containing aluminum salt. The soaking time is 15-60 minutes, wherein the effect is optimal in 15 minutes, 30 minutes or 60 minutes. In other embodiments, soaking with erbium-containing salt solution is also possible.
Step S140, fusing the base tube into an optical fiber prefabricated rod. In the process of fusing and shrinking the base tube into the optical fiber preform, the base tube doped with ytterbium is arranged on MCVD equipment, and the base tube is fused and shrunk into the optical fiber preform by high temperature, wherein the temperature range is 2000-2300 ℃, 2000 ℃, 2100 ℃ or 2300 ℃ and the effect is optimal.
The melting speed range of melting and shrinking the substrate tube into the optical fiber preform is 0.5mm/min-9 mm/min. Wherein the melt shrinkage speed can be 0.5mm/min, 2mm/min, 5mm/min or 9 mm/min. The loose glass body forms the rod core of the optical fiber preform rod in the preform rod manufacturing process, and the rod core forms the fiber core 1 of the optical fiber in the drawing process.
After the preform not doped with phosphorus was drawn into an optical fiber, the refractive index profile of the core was measured using an optical fiber radial refractive index profile measuring instrument, and the refractive index profile was measured as shown in FIG. 3. FIG. 3 is a schematic view of the radial refractive index profile of an optical fiber that is not doped with phosphorus. Wherein the abscissa of fig. 3 is the radial position of the cross-section of the optical fiber and the ordinate is the measured refractive index data.
After the preform doped with phosphorus is drawn into an optical fiber, the refractive index profile of the core is measured by using an optical fiber radial refractive index profile measuring instrument, and the refractive index profile is shown in fig. 4, where fig. 4 is a schematic view of the refractive index profile of the phosphorus-doped optical fiber in the radial direction. Wherein the abscissa of fig. 4 is the radial position of the cross-section of the optical fiber and the ordinate is the measured refractive index data. Comparing the experimental data of fig. 3 and 4, it is found that the central refractive index depression of the core of the large mode field ytterbium-doped fiber is reduced by doping phosphorus, and the stability and gain efficiency of the large mode field laser are improved.
The phosphorus-doped large-mode-field ytterbium-doped fiber is used for research and development of a fiber laser, and long-time practical application shows that compared with a phosphorus-undoped large-mode-field ytterbium-doped fiber, the background loss is reduced to some extent, and the photon darkening effect of the large-mode-field ytterbium-doped fiber is reduced.
Example three:
a method of making an optical fiber comprising the steps of:
step S100, polishing the inner wall of the base tube. During the polishing of the inner wall of the substrate tube, SF6 (sulfur hexafluoride) and oxygen were introduced into the interior of the substrate tube and the substrate tube was moved using a heating source. The chemical reaction of SF6 (sulfur hexafluoride) and oxygen inside the substrate tube generates HF (hydrogen fluoride), which is used for corroding the inner wall of the substrate tube to achieve the polishing effect of the inner wall of the substrate tube. Helium can be added into SF6 (sulfur hexafluoride) and oxygen to be input into the base tube, and the base tube is moved by using a heating source, so that the polishing effect of the inner wall of the base tube is achieved, and the inner wall of the base tube is favorably doped with phosphorus. Chlorine can also be added into the sulfur hexafluoride, and the chlorine can dry the inner wall of the base pipe to remove water molecules in the base pipe. Wherein the heating temperature is 1850-.
And step S110, doping phosphorus on the inner wall of the base pipe. In the process of doping phosphorus on the inner wall of the base tube, chloride enters the base tube from one end of the base tube by using oxygen or helium, the chloride is heated and reacts to generate loose glass body outside the base tube, and the glass body is deposited on the inner wall of the base tube. Chlorides include phosphorus oxychloride, silicon tetrachloride and germanium tetrachloride, which phosphorus oxychloride can also be another phosphorus compound. The glass body after reaction contains phosphorus element, so that the inner wall of the base tube can achieve the effect of phosphorus doping. The chemical formula of the reaction of heating and reacting the chloride to generate the glass body is as follows:
SiCl4+O2＝SiO2+2Cl2↑
GeCl4+O2＝GeO2+2Cl2↑
4POCl3+3O2＝2P2O5+6Cll2↑
and step S120, doping ytterbium on the inner wall of the base pipe. In the process of doping ytterbium on the inner wall of the base pipe, the loose vitreous body on the inner wall of the base pipe is soaked by using a solution containing ytterbium salt. Soaking with ytterbium-containing aluminum-containing salt solution is also possible. The soaking time is 15-60 minutes, wherein the effect is optimal in 15 minutes, 30 minutes or 60 minutes. In other instances, soaking with erbium-containing salt solutions is also possible.
Step S140, fusing the base tube into an optical fiber prefabricated rod. In the process of fusing and shrinking the base tube into the optical fiber preform, the base tube doped with ytterbium is arranged on MCVD equipment, and the base tube is fused and shrunk into the optical fiber preform by high temperature, wherein the temperature range is 2000-2300 ℃, 2000 ℃, 2100 ℃ or 2300 ℃ and the effect is optimal.
The melting speed range of melting and shrinking the substrate tube into the optical fiber preform is 0.5mm/min-9 mm/min. Wherein the melt shrinkage speed can be 0.5mm/min, 2mm/min, 5mm/min or 9 mm/min. Wherein the loose glass body forms the rod core of the optical fiber prefabricated rod in the manufacturing process of the prefabricated rod.
S160, drawing the optical fiber preform into an optical fiber. The optical fiber preform is drawn into an optical fiber using a draw tower apparatus. Wherein the rod core forms the core 1 of the optical fiber during drawing.
After the preform not doped with phosphorus was drawn into an optical fiber, the refractive index profile of the core was measured using an optical fiber radial refractive index profile measuring instrument, and the refractive index profile was measured as shown in FIG. 3. FIG. 3 is a schematic view of the radial refractive index profile of an optical fiber that is not doped with phosphorus. Wherein the abscissa of fig. 3 is the radial position of the cross-section of the optical fiber and the ordinate is the measured refractive index data.
After the preform doped with phosphorus is drawn into an optical fiber, the refractive index profile of the core is measured by using an optical fiber radial refractive index profile measuring instrument, and the refractive index profile is shown in fig. 4, where fig. 4 is a schematic view of the refractive index profile of the phosphorus-doped optical fiber in the radial direction. Wherein the abscissa of fig. 4 is the radial position of the cross-section of the optical fiber and the ordinate is the measured refractive index data. Comparing the experimental data of fig. 3 and 4, it is found that the central refractive index depression of the core of the large mode field ytterbium-doped fiber is reduced by doping phosphorus, and the stability and gain efficiency of the large mode field laser are improved.
The phosphorus-doped large-mode-field ytterbium-doped fiber is used for research and development of a fiber laser, and long-time practical application shows that compared with a phosphorus-undoped large-mode-field ytterbium-doped fiber, the background loss is reduced to some extent, and the photon darkening effect of the large-mode-field ytterbium-doped fiber is reduced.
Example four:
as shown in fig. 2, a method for preparing an optical fiber includes the following steps:
s100, doping phosphorus into the fiber core 1 of the base tube. Chloride enters the interior of the base tube from one end of the base tube by using oxygen, and is heated outside the base tube, the chloride in the base tube is heated and reacts to generate a loose glass body, and the glass body is deposited on a fiber core 1 of the base tube. Chlorides include phosphorus oxychloride, silicon tetrachloride and germanium tetrachloride, which phosphorus oxychloride can also be another phosphorus compound. The glass body after reaction contains phosphorus element, so that the fiber core 1 of the base tube achieves the effect of phosphorus doping. The chemical formula of the reaction of heating and reacting the chloride to generate the glass body is as follows:
SiCl4+O2＝SiO2+2Cl2↑
GeCl4+O2＝GeO2+2Cl2↑
4 POCl3+3O2＝2P2O5+6 Cl2↑
s120, doping ytterbium in the fiber core 1 of the base tube. And after the base pipe doped with phosphorus is cooled, taking the base pipe down from MCVD equipment, and soaking the glass body of the fiber core 1 of the base pipe in ytterbium salt solution for 15-60 minutes, wherein the soaking time of 15 minutes, 30 minutes or 60 minutes is more favorable for the fiber core 1 of the base pipe to achieve the phosphorus-doped effect.
S140, fusing the base tube into an optical fiber prefabricated rod. The base tube after being doped with ytterbium is installed on MCVD equipment, and the base tube is fused into the optical fiber prefabricated rod at high temperature, wherein the temperature range can be 2000-2300 ℃, and the temperature effect at 2000 ℃, 2100 ℃ or 2300 ℃ is the best. The melting speed range of melting and shrinking the substrate tube into the optical fiber preform is 0.5mm/min-9 mm/min. Wherein the melt shrinkage speed can be 0.5mm/min, 2mm/min, 5mm/min or 9 mm/min. Wherein the loose glass body forms the rod core of the optical fiber prefabricated rod in the manufacturing process of the prefabricated rod.
S160, drawing the optical fiber preform into an optical fiber. The optical fiber preform is drawn into an optical fiber using a draw tower apparatus. Wherein the rod core forms the core 1 of the optical fiber during drawing.
After the preform not doped with phosphorus is drawn into an optical fiber, the fiber core is tested for the relevant refractive index profile using a fiber radial refractive index profile tester. FIG. 3 is a schematic view of the radial refractive index profile of an optical fiber that is not doped with phosphorus. Wherein the abscissa of fig. 3 is the radial position of the cross-section of the optical fiber and the ordinate is the measured refractive index data.
After the preform doped with phosphorus is drawn into an optical fiber, the refractive index profile obtained by testing the core using an optical fiber radial refractive index profile testing instrument is shown in fig. 4, and fig. 4 is a schematic view of the radial refractive index profile of the optical fiber doped with phosphorus. Wherein the abscissa of fig. 4 is the radial position of the cross-section of the optical fiber and the ordinate is the measured refractive index data. Comparing the experimental data of fig. 3 and 4, it is found that the central refractive index depression of the core of the large mode field ytterbium-doped fiber is reduced by doping phosphorus, and the stability and gain efficiency of the large mode field laser are improved.
As shown in fig. 5, the large mode field ytterbium-doped fiber includes a fiber core 1, an inner cladding 2, an outer cladding 3 and a protective layer 4, and the phosphorus-doped fiber of the present invention may be a substrate tube with phosphorus-doped inner wall or a substrate tube with phosphorus-doped outer wall.
The laser gain of the optical fiber is proportional to the number of the turnover particles contained in the optical fiber, and therefore the laser gain of the optical fiber is also proportional to the number of rare earth ions in the optical fiber. In order to obtain a sufficiently high laser gain, the doping amount of rare-earth ions needs to be increased in the optical fiber, thereby increasing the laser output power of the optical fiber. However, the higher the concentration of rare earth ions in the optical fiber, the more easily the photodarkening effect is caused, and the photodarkening effect is an induced absorption loss phenomenon and can cause the permanent increase of the background loss of the doped optical fiber core layer. The phosphorus-doped large-mode-field ytterbium-doped fiber is used for research and development of a fiber laser, and long-time practical application shows that compared with a phosphorus-undoped large-mode-field ytterbium-doped fiber, the background loss is reduced to some extent, and the photon darkening effect of the large-mode-field ytterbium-doped fiber is reduced.
According to the "Oxygen Defect (ODC) color center" theory, oxygen defect color centers in Yb3+ (ytterbium ions) doped aluminosilicates can result in short wavelength energy being absorbed by the oxygen defect color center, causing energy losses at ultraviolet and infrared wavelengths. When the number of ytterbium ions exceeds the number of holes in the quartz base, the probability of breaking the valence bond between Yb-Yb (ytterbium) increases (due to the lack of oxygen ions), that is, Yb-ODC. Yb-ODC releases a free electron through two-photon absorption, and after the free electron is captured by Yb (ytterbium), the Yb-ODC can form a color center, and the color center absorbs photons with certain energy to cause energy loss and power reduction.
The reason that the phosphorus doped with phosphorus can better inhibit the photodarkening effect is that the phosphorus with the valence of +5 and the high valence state can not only combine more oxygen to inhibit the formation of color centers, but also the solubility of ytterbium ions in silicon and phosphorus matrixes is higher, and meanwhile, the phosphorus with the long bond can disperse ytterbium more easily to reduce clusters, so that the formation of the color centers is reduced, the energy loss and the power reduction caused by the fact that the color centers absorb photons with certain energy are also reduced, and the photodarkening effect of the large-mode-field ytterbium-doped optical fiber is further reduced.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A method for preparing an optical fiber preform is characterized by comprising the following steps:
doping phosphorus on the inner wall of the base pipe;
doping ytterbium on the inner wall of the base pipe;
the substrate tube is fused into an optical fiber preform.
2. The method of claim 1, wherein the step of "doping the inner wall of the substrate tube with phosphorus" comprises the steps of: the method comprises the steps of enabling chloride to enter the interior of a base pipe from one end of the base pipe through oxygen, heating the interior of the base pipe, heating the chloride in the base pipe to react to generate a glass body, and depositing the glass body on the inner wall of the base pipe.
3. The method of fabricating an optical fiber preform of claim 2 wherein the chlorides include phosphorus oxychloride, silicon tetrachloride, and germanium tetrachloride.
4. The method for fabricating an optical fiber preform according to claim 1, wherein the step of "ytterbium doping an inner wall of the substrate tube" specifically comprises the steps of: the vitreous body of the inner wall of the substrate tube is soaked by using a solution containing ytterbium salt.
5. A method for fabricating an optical fiber preform according to claim 1, wherein the inner wall of the substrate tube is polished before the step of "doping the inner wall of the substrate tube with phosphorus".
6. The method for fabricating an optical fiber preform according to claim 5, wherein the step of "polishing the inner wall of the substrate tube" specifically comprises the steps of: using SF6And oxygen is introduced into the interior of the substrate tube and the substrate tube is moved using a heating source.
7. The method for fabricating an optical fiber preform according to claim 6, wherein the temperature of the heating source is 1850-.
8. The method of claim 1, wherein the step of collapsing the substrate tube into the optical fiber preform comprises the steps of: the base tube after being doped with ytterbium is installed on the improved chemical vapor deposition equipment and is fused into the optical fiber prefabricated rod at 2000-2300 deg.c.
9. A method for producing an optical fiber, comprising the method for producing an optical fiber preform according to any one of claims 1 to 8, further comprising the steps of: the optical fiber preform is drawn into an optical fiber.
10. An optical fiber, wherein the optical fiber is the optical fiber obtained by the method for producing an optical fiber according to claim 9.
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