CN110395901B - High-attenuation optical fiber and preparation method thereof - Google Patents
High-attenuation optical fiber and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a high-attenuation optical fiber and a preparation method thereof. The core layer of the high-attenuation optical fiber has a step-type structure in the section of the refractive index of the cladding layer, the change rate of the refractive index of the fiber core is between 1% and 15%, the core layer contains more than two metal elements with unfilled valence layer d orbits, and the metal elements are transition metal elements in groups 4 to 10 in the periodic table of the elements. The method comprises the following steps: (1) mixing a first phase containing metal elements according to a formula ratio with a second phase taking loose quartz glass powder as a main component to prepare a uniform solid phase; (2) preparing a solid transparent glass body by taking a uniform solid phase as a raw material; (3) and taking the solid transparent glass body as an optical fiber preform core rod to prepare a high-attenuation optical fiber preform and drawing the high-attenuation optical fiber preform into the high-attenuation optical fiber. The invention has flat attenuation spectrum and good stability in O, E, S, C, L waveband of optical fiber communication, can meet the application requirements of optical fiber communication network, optical fiber data network, optical fiber CATV network and optical fiber test system, and improves the system performance.
Description
Technical Field
The invention belongs to the field of optical fiber devices, and particularly relates to a high-attenuation optical fiber and a preparation method thereof, wherein the optical fiber has a higher attenuation coefficient and a better attenuation flatness within the wavelength range of 1250 nm-1625 nm, and an attenuator made of the optical fiber is used for reducing the optical signal power of a communication system so as to meet the detection condition of a photoelectric detector.
Background
With the development of 5G network technology application and the increasing demand of people for broadband transmission, optical communication systems are developing towards long distance, high capacity and high rate. Fiber optic transmission rates range from the first megabits per second (Mbps) to now as high as 100 gbits per second, and even 400 gbits per second. In order to meet the long-distance transmission requirement, an optical fiber amplifier is often used in the optical communication system, thereby increasing the transmission power and the transmission distance. However, on the other hand, the higher optical power may exceed the detection range of the photodetector, and therefore, a passive device attenuator is required to reduce the signal optical power to a suitable range.
Attenuators can be classified into various types according to the working principle: air isolation technology, displacement dislocation technology, attenuation optical fiber technology, absorption glass method, solid state light attenuation technology, and combination of two or more technologies. The attenuation optical fiber technology is characterized in that metal ions are doped into a fiber core according to the fact that the metal ions have a strong absorption effect on light, so that the optical fiber has a high attenuation coefficient, is used for calibrating and correcting debugging optical power performance and debugging optical fiber instruments in an optical communication system, and avoids distortion generated by an optical receiver due to the fact that input optical power is too strong.
In the prior art, an MCVD solution adding method is generally adopted to prepare the attenuation optical fiber, and the principle of the method is that MCVD powder gaps absorb metal ion solution and then are sintered into a solid preform. MCVD technology adopts an external heat source to heat a glass tube, so that reaction gas is deposited into porous powder, wherein the shape, size and distribution of pores are extremely complex and difficult to accurately control; the influence deviation of the powder particle size by the reaction temperature is large, and the temperature difference of 200 ℃ or even 300 ℃ in a reaction area can be brought by the wall thickness of the glass liner tube and the thickness deviation of a deposition layer by one millimeter, so that the characteristics of the powder particle size, the shape and the like are influenced. The subsequent solution viscosity, concentration and soaking time can influence the absorption of the solution by the pores. During the sintering process, the metal particles absorbed by the core area of the core rod are easy to be lost due to the flowing and corrosion action of high-temperature gas in the tube, and the loss is inevitable and uncontrollable.
High quality attenuation optical fibers are required to have a high attenuation coefficient in the wavelength range of 1250nm to 1625nm, and the difference in attenuation coefficient between the respective wavelengths in this range is as small as possible, that is, the degree of flatness of the attenuation spectrum of the optical fiber in the above wavelength range is as small as possible. The prior art does not better solve the problem of considering both higher attenuation coefficient values and smaller attenuation coefficient differences.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides a high-attenuation optical fiber and a preparation method thereof, and aims to adjust the flatness of an attenuation spectrum of the high-attenuation optical fiber in a specific wavelength range and the change rate of the section refractive index of the optical fiber core layer by selecting the doping element type of the optical fiber core layer and accurately controlling the doping amount, so that the technical problems of low flatness of the attenuation spectrum of the high-attenuation optical fiber, low attenuation coefficient of the optical fiber and high change rate of the section refractive index are solved, the consumption of the attenuation optical fiber type attenuator to the optical fiber is measured by centimeters or even millimeters, and the requirement of a passive optical electronic device to the high-attenuation optical fiber is met.
To achieve the above object, according to one aspect of the present invention, there is provided a high attenuation optical fiber having a step-type structure in the core refractive index profile, the core refractive index having a rate of change of not more than 15%, the core containing one or more metal elements having an unfilled d-orbital in the valence domain, the metal elements being in the periodic table
To
A group transition metal element.
Preferably, the high attenuation optical fiber has a rate of change of the core refractive index within 10%.
Preferably, the core layer of the high attenuation optical fiber contains two metal elements, specifically:
a metal element having an absorption coefficient of a negative slope in a target wavelength range, in terms of mass percentage, of 0 to 5.20 mol%; and
and 0-2.45 mol% of a metal element having an absorption coefficient of a positive slope in a target wavelength range in terms of mass%.
Preferably, in the high attenuation optical fiber, the metal element having an absorption coefficient with a negative slope in a wavelength range of 1250nm to 1625nm contained in the core layer includes iron, chromium, manganese, vanadium, and the like.
Preferably, in the high attenuation optical fiber, the metal element having an absorption coefficient with a positive slope in a wavelength range of 1250nm to 1625nm contained in the core layer includes cobalt, nickel, or the like. Preferably, the high-attenuation optical fiber comprises 0-13 mol% of aluminum element and/or 0-20 mol% of germanium in terms of mass percentage.
Preferably, the attenuation coefficient of the high-attenuation optical fiber in the wavelength range of 1250nm to 1625nm is more than 0.5 dB/cm.
Preferably, the attenuation spectrum of the high attenuation optical fiber at O, E, S, C, L waveband of optical fiber communication is flat, and the attenuation flatness is within 10%, preferably within 5%.
According to another aspect of the present invention, there is provided a method for preparing a high attenuation optical fiber, comprising the steps of:
(1) mixing a first phase containing metal elements according to a formula ratio with a second phase taking loose quartz glass powder as a main component to prepare a uniform solid phase; wherein the first phase is a liquid phase and/or a solid phase, and the density of the quartz glass powder is 0.3-1.1 g/cm3；
(2) Preparing a solid transparent glass body by using the uniform solid phase obtained in the step (1) as a raw material;
(3) and (3) taking the solid transparent glass body obtained in the step (2) as an optical fiber preform core rod to prepare a high-attenuation optical fiber preform and drawing the high-attenuation optical fiber provided by the invention.
Preferably, in the method for preparing the high attenuation optical fiber, the first phase in step (1) is a liquid phase containing two or more of cobalt ions, iron ions, chromium ions, manganese ions and nickel ions.
Preferably, in the preparation method of the high attenuation optical fiber, the loose quartz glass powder in the step (1) is prepared by a chemical vapor deposition process.
Preferably, in the method for manufacturing the high attenuation optical fiber, the loose silica glass powder in step (1) contains germanium element in a formula ratio. In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
the high-attenuation optical fiber provided by the invention has high attenuation flatness in a specific wavelength range and small change rate of the section refractive index, so that the attenuation quantity is high in precision and good in stability, the application requirements of an optical fiber communication network, an optical fiber data network, an optical fiber CATV network and an optical fiber test system can be met, and the transmission and receiving performance of the system is improved.
According to the preparation method of the high-attenuation optical fiber, metal elements needing to be doped are doped with quartz glass in a liquid phase or solid phase mode, the loss of the doped elements is small in the rod-making and wire-drawing process, the doping amount is accurate and controllable, the consistency of the refractive index of the section of the manufactured optical fiber is high, the technical problem that the attenuation performance of the optical fiber is unstable and uneven due to large change of the refractive index of the section of the optical fiber in the prior art is solved, and the cost is low.
Drawings
FIG. 1 is a cross-sectional view of the refractive index of a preform for an optical fiber provided in example 1 of the present invention;
FIG. 2 is a cross-sectional view of the refractive index of a preform for an optical fiber provided in example 2 of the present invention;
FIG. 3 is a cross-sectional view of the refractive index of a preform for an optical fiber provided in example 3 of the present invention;
FIG. 4 is a cross-sectional view showing the refractive index of an optical fiber provided in example 4 of the present invention;
FIG. 5 is a cross-sectional view showing the refractive index of an optical fiber provided in example 5 of the present invention;
FIG. 6 is a cross-sectional view showing the refractive index of an optical fiber provided in example 6 of the present invention.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: the abscissa represents the cross-sectional radius of the optical fiber or its preform, and the ordinate represents the refractive index difference of the optical fiber or its preform.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Some of the terms used in the present invention are defined as follows:
deposition: the process comprises the steps of reacting raw materials of the optical fiber under certain physical and chemical conditions to generate doped or pure quartz glass;
refractive index profile: the relationship curve between the refractive index of the optical fiber on the section perpendicular to the axial direction and the section radius of the optical fiber;
and (3) OVD: an outside vapor deposition method;
VAD: axial vapor deposition;
MCVD: modified chemical vapor deposition;
NA: numerical aperture;
attenuation flatness degree: the ratio of the maximum to minimum difference to the maximum of the attenuation coefficient of the optical fiber over a particular wavelength range, in percent;
rate of change of refractive index: the ratio of the difference between the maximum and minimum values of the refractive index of the core of the optical fiber to the maximum value, in percent.
The invention provides a high-attenuation optical fiber, wherein the refractive index profile of a core layer is of a step structure, the change rate of the refractive index of the core is between 1% and 15%, preferably within 10%, and more preferably within 5%; the attenuation coefficient of the wavelength range of 1250 nm-1625 nm is more than 0.5dB/cm, and the preferred attenuation coefficient is more than 1 dB/cm; more preferably the attenuation coefficient is greater than 3 dB/cm; more preferably, the attenuation coefficient is 3dB/cm to 30 dB/cm.
The high attenuation optical fiber preferably has an NA of 0.06 to 0.18. The attenuation spectrum in the O, E, S, C, L waveband of optical fiber communication is flat, and the attenuation flatness is within 10%, preferably within 5%.
The core layer contains one or more metal elements, preferably two or more metal elements, the valence layer d orbitals of the metal elements are not filled, and the metal elements are transition metal elements of groups 4 to 10 in the periodic table. Wherein the metal element is a metal element with an absorption coefficient of a negative slope in a target wavelength range, and the metal element contains 0-5.20 mol% in terms of the mass percentage of the substance; or the metal element is a metal element having an absorption coefficient of a negative slope in a target wavelength range and is contained in an amount of 0 to 2.45mol% in terms of the mass percentage. When the core layer contains a plurality of the metal elements, it is preferable to include at least one metal element having an absorption coefficient with a negative slope in the target wavelength range, and to include at least one metal element having an absorption coefficient with a negative slope in the target wavelength range. Preferably, the core layer contains 0-13 mol% of aluminum element and/or 0-20 mol% of germanium. The metal element of the unfilled valence layer d orbit is selected from cobalt element, iron element, chromium element, manganese element and nickel element; preferably:
the content of cobalt element in the core layer of the high attenuation optical fiber is 0-2.30 mol%, preferably 0.03-2.10 mol%, more preferably 0.30-1.90 mol%, and more preferably 0.60-1.90 mol% calculated by the amount percentage of the substance;
the content of iron element in the core layer of the high attenuation optical fiber is 0-1.05 mol%, preferably 0.02-1.05 mol%, more preferably 0.10-1.05 mol%, and more preferably 0.20-0.80 mol% calculated by the amount percentage of the substance;
the content of chromium element in the core layer of the high attenuation optical fiber is 0 to 1.60mol%, preferably 0.18 to 1.60mol%, more preferably 0.30 to 1.60mol%, and still more preferably 0.49 to 1.60mol% calculated by the amount percentage of the substance;
the content of manganese element in the core layer of the high attenuation optical fiber is 0 to 0.80mol%, preferably 0.02 to 1.25mol%, more preferably 0.10 to 1.05mol%, and more preferably 0.26 to 0.80mol% calculated by the amount percentage of the substance;
the content of nickel element in the core layer of the high attenuation optical fiber is 0-2.90 mol%, preferably 0.30-2.90 mol%, more preferably 0.30-1.90 mol%, and more preferably 0.60-1.90 mol% calculated by the amount percentage of the substance;
the core layer of the high attenuation optical fiber also contains aluminum element, and the content of the aluminum element is 0-13 mol%, preferably 0-4.30 mol%, more preferably 0.02-3.00 mol%, and more preferably 0.02-1.50 mol% calculated by the amount percentage of the substance; the addition of the aluminum element can reduce the volatilization loss of other metal elements during doping, and ensure the controllability of the doping amount, thereby ensuring the stable and uniform light attenuation performance of the whole fiber core and having the function of adjusting the refractive index.
The core layer of the high attenuation optical fiber also contains germanium element, and the content of the germanium element is 0-20 mol%, preferably 0-5.30 mol%, more preferably 0.02-3.00 mol%, and more preferably 0.85-2.50 mol% calculated by the amount percentage of the substance; the addition of germanium element can adjust the refractive index of the fiber core to optimize the NA value, thereby reducing the change rate of the refractive index and increasing the uniformity.
The preparation method of the high-attenuation optical fiber provided by the invention comprises the following steps:
(1) mixing a first phase containing metal elements according to a formula ratio with a second phase taking loose quartz glass powder as a main component to prepare a uniform solid phase; wherein the first phase is a liquid phase and/or a solid phase, and the density of the quartz glass powder is 0.3-1.1 g/cm3。
Preferably, the first phase is a liquid phase containing two or more of cobalt ions, iron ions, chromium ions, manganese ions and nickel ions;
the loose quartz glass powder is prepared by adopting a chemical vapor deposition process, and the germanium element with the formula proportion is preferably selected. Chemical vapor deposition processes include VAD, MCVD, or OVD processes.
The loose quartz glass powder prepared by adopting the chemical vapor deposition process is white opaque silicon dioxide; the quartz glass powder is loose, contains a large number of gaps, can be doped by two phases suitable for the quartz glass powder provided by the invention, and has the density of 0.3-1.1 g/cubic centimeter, preferably 0.3-0.7 g/cubic centimeter, and more preferably 0.4-0.6 g/cubic centimeter.
(2) Preparing a solid transparent glass body by using the uniform solid phase obtained in the step (1) as a raw material;
(3) and (3) taking the solid transparent glass body obtained in the step (2) as an optical fiber preform core rod to prepare a high-attenuation optical fiber preform and drawing the high-attenuation optical fiber provided by the invention. Specifically, the method comprises the following steps:
the core rod is arranged in a corresponding quartz sleeve to form a high-attenuation optical fiber prefabricated rod; or the quartz glass cladding is made outside the core rod by an external deposition method/external spraying method so as to reach the proper proportion of the fiber core and the cladding to form a high-attenuation optical fiber prefabricated rod,
preferably, the drawing process is as follows:
and melting and drawing the high-attenuation optical fiber preform into a high-attenuation optical fiber with the cladding diameter of about 125 microns at the high temperature of about 1700-2200 ℃, wherein the cladding diameter is preferably 125 microns +/-2 microns.
At present, the preparation method of the high-attenuation optical fiber adopts the MCVD technology, and the technology has the inevitable, uncontrollable and unknown loss in the doping process due to the fact that metal particles have inevitable, uncontrollable and unknown loss, so that the technology has poor portability, namely, the preparation conditions cannot be completely the same, the loss in the doping process has unknown difference under different instrument and equipment conditions, and finally, the production process cannot be expanded, the product consistency is poor, and the performance difference between different batches is uncontrollable. Therefore, the invention adopts a two-phase doping sintering technology, metal particles are mixed by a liquid phase and/or a solid phase and a second phase which takes loose quartz glass powder as a main component, and finally a solid-phase doped raw material is formed, so that the loss of the metal particles is small and even negligible, and the loss is controllable; the method has good reproducibility, convenient transplantation, good product consistency and controllable quality.
The following are examples:
the core element content and the main performance parameters of the prepared high attenuation optical fiber in the examples are shown in table 1.
Table 1 examples core element content and main performance parameters
The preparation methods of the optical fibers in the examples are respectively as follows:
example 1
OVD (outside vapor deposition) is adopted to deposit quartz powder, and the powder is prepared from silicon tetrachloride, germanium tetrachloride and O2And C2F6The reaction gas is heated by a heat source such as oxyhydrogen flame to carry out chemical reaction, and opaque white silicon dioxide powder with the density of 0.4 to 0.7 g/cubic centimeter is generated. Then, cobalt, iron and chromium salts with corresponding mass are weighed according to the molar ratio, fully dissolved in water or alcohol solution, and then mixed with silicon dioxide powder with corresponding mass ratio and uniformly dispersed. Drying by removing free water under heating with microwave radiation preferably for a certain time0.1min to 30min, the frequency range of the microwave is 1.0GHz to 2.45GHz, and the radiation power of the microwave is 0.5kW to 10 kW. After drying, the silica powder having absorbed the metal salt is sufficiently ground, mixed, and then isostatically pressed into a dense powder having a density of 1.1 to 2.1 g/cc, preferably 1.7 to 2.1 g/cc, and then sintered into a solid silica glass core rod. And assembling the core rod and a quartz sleeve with a corresponding size to form a high-attenuation optical fiber preform, and then carrying out melt drawing on the high-attenuation optical fiber preform at the high temperature of about 1700-2200 ℃ to form a high-attenuation optical fiber with the cladding diameter of about 125 microns, wherein the preferred cladding diameter is 125 microns +/-2 microns.
The optical fiber has a step-type structure, the cross section of the refractive index of a preform is shown in figure 1, the change rate of the refractive index of a core layer is within 4%, and the optical fiber has high precision and high stability when the attenuator is manufactured due to excellent refractive index flatness. The average attenuation coefficient of the optical fiber at the wavelength of 1550nm is 0.497dB/cm, the optical fiber has flat absorption characteristics in the wavelength range of 1250 nm-1625 nm, and the attenuation flatness of the optical fiber is within 4 percent.
Example 2
MCVD (modified chemical vapor deposition) is adopted to deposit quartz powder, and the powder is prepared from silicon tetrachloride, germanium tetrachloride and O2And C2F6The reaction gas is heated by oxyhydrogen flame and other heat sources to generate chemical reaction in the tube, and opaque white silicon dioxide powder with the density of 0.3 to 0.7 g/cubic centimeter is generated. Taking out the powder, weighing cobalt, iron, chromium and aluminum salts with corresponding mass according to molar ratio, fully dissolving the cobalt, iron, chromium and aluminum salts in water or alcohol solution, mixing the solution with silicon dioxide powder with corresponding mass ratio, and uniformly dispersing the mixture. And then heating by microwave radiation to remove free water for drying, wherein the microwave radiation time is preferably 0.1min to 10min, the frequency range of the microwave is 1.0GHz to 2.45GHz, and the microwave radiation power is 0.5kW to 5 kW. After drying, the silica powder having absorbed the metal salt is sufficiently ground, mixed, and then isostatically pressed into a dense powder having a density of 1.1 to 2.1 g/cc, preferably 1.7 to 2.1 g/cc, and then sintered into a solid silica glass core rod. Then the core rod is combined with a quartz sleeve with corresponding sizeAssembling to form a high attenuation optical fiber preform, and then melting and drawing the high attenuation optical fiber preform into a high attenuation optical fiber with the cladding diameter of about 125 microns at the high temperature of about 1700-2200 ℃, wherein the preferred cladding diameter is 125 microns +/-1 micron.
The optical fiber has a step-type structure, the cross section of the refractive index of a preform is shown in figure 2, the change rate of the refractive index of a core layer is within 4%, and the optical fiber has high precision and high stability when the attenuator is manufactured due to excellent refractive index flatness. The average attenuation coefficient of the optical fiber at the wavelength of 1550nm is 2.78dB/cm, the optical fiber has flat absorption characteristics in the wavelength range of 1250nm to 1625nm, and the attenuation flatness of the optical fiber is within 4 percent.
Example 3
OVD (outside vapor deposition) is adopted to deposit quartz powder, and the powder is prepared from octamethylcyclotetrasiloxane, germanium tetrachloride and O2And C2F6The reaction gas is heated by a heat source such as oxyhydrogen flame to carry out chemical reaction, and opaque white silicon dioxide powder with the density of 0.4 to 0.6 g/cubic centimeter is generated. Taking down the powder, weighing cobalt, chromium and aluminum salt with corresponding mass according to molar ratio, fully dissolving the cobalt, chromium and aluminum salt in water or alcohol solution, mixing the cobalt, chromium and aluminum salt with the silicon dioxide powder with corresponding mass proportion, and uniformly dispersing the mixture. And then heating by microwave radiation to remove free water for drying, wherein the microwave radiation time is preferably 0.1min to 10min, the frequency range of the microwave is 1.0GHz to 2.45GHz, and the microwave radiation power is 0.5kW to 5 kW. After drying, the silica powder having absorbed the metal salt is sufficiently ground, mixed, and then isostatically pressed into a dense powder having a density of 1.1 to 2.1 g/cc, preferably 1.7 to 2.1 g/cc, and sintered under vacuum into a solid silica glass core rod. And assembling the core rod and a quartz sleeve with a corresponding size to form a high-attenuation optical fiber preform, and then carrying out melt drawing on the high-attenuation optical fiber preform at the high temperature of about 1700-2200 ℃ to form a high-attenuation optical fiber with the cladding diameter of about 125 microns, wherein the preferred cladding diameter is 125 microns +/-1 micron.
The optical fiber has a step-type structure, the cross section of the refractive index of a preform is shown in figure 3, the change rate of the refractive index of a core layer is within 4%, and the optical fiber has high precision and high stability when the attenuator is manufactured due to excellent refractive index flatness. The average attenuation coefficient of the optical fiber at the wavelength of 1550nm is 3.85dB/cm, the optical fiber has flat absorption characteristics in the wavelength range of 1250nm to 1625nm, and the attenuation flatness of the optical fiber is within 5 percent.
Example 4
OVD (outside vapor deposition) is adopted to deposit quartz powder, and the powder is prepared from octamethylcyclotetrasiloxane, germanium tetrachloride and O2And C2F6The reaction gas is heated by a heat source such as oxyhydrogen flame and the like to carry out chemical reaction to generate opaque white silicon dioxide powder, and the density of the opaque white silicon dioxide powder is 0.4 to 0.55 g/cubic centimeter. Taking down the powder, and weighing nanoparticles of cobalt, nickel, manganese and aluminum salt, such as chloride or nitrate, with corresponding mass according to molar ratio, wherein the cross section size of the nanoparticles is more than 20 nanometers, preferably more than 50 nanometers, more preferably more than 100 nanometers, more preferably more than 150nm, more preferably more than 200 nanometers, or 25-500 nanometers, preferably 50-400 nanometers, more preferably 50-300 nanometers, preferably 50-200 nanometers, or 100-400 nanometers, or 100-300 nanometers. The metal salt nano-particles can absorb light power and reflect light power in the fiber core of the optical fiber, so that a part of light power leaks from the cladding or returns to the fiber core to be absorbed, and the randomly distributed nano-particles play a role in homogenizing the attenuation of light with different wavelengths, thereby further flattening the light attenuation characteristic in the wavelength range of 1250nm to 1625 nm. Fully grinding and homogenizing the silicon dioxide powder mixed with the metal salt nano particles, then performing isostatic pressing to obtain compact powder with the density of 1.8 g/cubic centimeter, and sintering to obtain the solid quartz glass core rod. And then preparing a quartz glass cladding from the core rod by adopting an external spraying method to form a high-attenuation optical fiber preform, and then carrying out melt drawing on the high-attenuation optical fiber preform at the high temperature of about 1750 ℃ to form a high-attenuation optical fiber with the cladding diameter of about 125 microns, wherein the preferred cladding diameter is 125 microns +/-1 micron.
The optical fiber has a step-type structure, the cross section of the refractive index of the optical fiber is shown in fig. 4, the change rate of the refractive index of a core layer is within 4%, and the optical fiber has high precision and high stability when the attenuator is manufactured due to excellent refractive index flatness and nano-particle doping of the fiber core. The average attenuation coefficient of the optical fiber at the wavelength of 1550nm is 8.75dB/cm, the optical fiber has flat absorption characteristics in the wavelength range of 1250nm to 1625nm, and the attenuation flatness of the optical fiber is within 5 percent.
Example 5
OVD (outside vapor deposition) is adopted to deposit quartz powder, and the powder is prepared from octamethylcyclotetrasiloxane, germanium tetrachloride and O2And C2F6The reaction gas is heated by a heat source such as oxyhydrogen flame and the like to carry out chemical reaction to generate opaque white silicon dioxide powder, and the density of the opaque white silicon dioxide powder is 0.50 to 0.55 g/cubic centimeter. Taking off the powder, weighing cobalt, nickel, iron, chromium and aluminum salt with set mass, fully dissolving the cobalt, nickel, iron, chromium and aluminum salt in water or alcohol solution, mixing the powder with silicon dioxide powder with corresponding mass proportion and uniformly dispersing the powder, and heating the powder by microwave radiation to remove free water for drying. Then, nanoparticles of the above metal salt are added to the mixture, the nanoparticles having a cross-sectional size of more than 20 nm, preferably more than 50nm, more preferably more than 100 nm, more preferably more than 150nm, more preferably more than 200 nm, or 25 to 500 nm, preferably 50 to 400 nm, more preferably 50 to 300 nm, preferably 50 to 200 nm, or 100 to 400 nm, or 100 to 300 nm. The metal salt nano particles can absorb light power and reflect light power in the fiber core of the optical fiber, and the randomly distributed nano particles play a role in homogenizing the attenuation of light with different wavelengths, so that the light attenuation characteristic in the wavelength range of 1250nm to 1625nm is further flattened. After drying, the silicon dioxide powder absorbed with the metal salt is matched with the metal salt nano-particles according to the mol ratio to ensure that the content of the total metal salt is in accordance with the set value, then the materials are fully ground and mixed, and then the mixture is subjected to isostatic pressing to be compressed into dense powder with the density of 2.0 g/cubic centimeter, and the dense powder is sintered into the solid quartz glass core rod under vacuum. And then, preparing a quartz glass cladding from the core rod by adopting an OVD method to form a high-attenuation optical fiber preform, and then carrying out melt drawing on the high-attenuation optical fiber preform at the high temperature of 1800 ℃ to form a high-attenuation optical fiber with the cladding diameter of about 125 microns, wherein the preferred cladding diameter is 125 microns +/-1 micron.
The optical fiber has a step-type structure, the cross section of the refractive index of the optical fiber is shown in fig. 5, the change rate of the refractive index of the core layer is within 5%, and the optical fiber has high precision and high stability when the attenuator is manufactured due to the excellent flatness of the refractive index. The average attenuation coefficient of the optical fiber at the wavelength of 1550nm is 15.31dB/cm, the optical fiber has flat absorption characteristics in the wavelength range of 1250nm to 1625nm, and the attenuation flatness of the optical fiber is within 5 percent.
Example 6
OVD (outside vapor deposition) is adopted to deposit quartz powder, and the powder is prepared from octamethylcyclotetrasiloxane, germanium tetrachloride and O2And C2F6The reaction gas is heated by a heat source such as oxyhydrogen flame and the like to carry out chemical reaction to generate opaque white silicon dioxide powder, and the density of the opaque white silicon dioxide powder is 0.50 to 0.55 g/cubic centimeter. Taking down the powder, weighing cobalt, iron, chromium and aluminum salts with corresponding mass according to molar ratio, fully dissolving the cobalt, iron, chromium and aluminum salts in water or alcohol solution, mixing the solution with silicon dioxide powder with corresponding mass ratio, and uniformly dispersing the mixture. And then heating by microwave radiation to remove free water for drying, wherein the microwave radiation time is preferably 1min to 10min, the frequency range of the microwave is 1.0GHz to 2.45GHz, and the microwave radiation power is 0.5kW to 5 kW. After drying, the silica powder having absorbed the metal salt was sufficiently ground, mixed, and then isostatically pressed into a dense powder having a density of 2.0 g/cc, and sintered in vacuum into a solid quartz glass core rod. And then, preparing a quartz glass cladding from the core rod by adopting an OVD method to form a high-attenuation optical fiber preform, and then carrying out melt drawing on the high-attenuation optical fiber preform at the high temperature of 1800 ℃ to form a high-attenuation optical fiber with the cladding diameter of about 125 microns, wherein the preferred cladding diameter is 125 microns +/-1 micron.
The optical fiber has a step-type structure, the cross section of the refractive index of the optical fiber is shown in fig. 6, the change rate of the refractive index of the core layer is within 5%, and the optical fiber has high precision and high stability when the attenuator is manufactured due to the excellent flatness of the refractive index. The average attenuation coefficient of the optical fiber at the wavelength of 1550nm is 30.13dB/cm, the optical fiber has flat absorption characteristics in the wavelength range of 1250nm to 1625nm, and the attenuation flatness of the optical fiber is within 6 percent.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A high attenuation optical fiber is characterized in that the refractive index profile of a core layer is of a step structure, the change rate of the refractive index of the core is not more than 15%, and the change rate of the refractive index refers to the ratio of the difference between the maximum value and the minimum value of the refractive index of the core layer of the optical fiber to the maximum value, and is counted by percentage; the core layer contains a plurality of metal elements, valence layer d orbitals of the metal elements are not filled, and the metal elements are in the periodic table of the elements
To
A group transition metal element; the core layer contains two types of metal elements, specifically:
a metal element having an absorption coefficient of a negative slope in a target wavelength range, in terms of mass percentage, of 0 to 5.20 mol%; and
and 0-2.45 mol% of a metal element having an absorption coefficient of a positive slope in a target wavelength range in terms of mass%.
2. The high attenuation optical fiber according to claim 1, wherein the rate of change of the core refractive index is within 10%.
3. The high attenuation optical fiber according to claim 1, wherein said core layer contains two of said metal elements, and is made of:
nanoparticles of cobalt, nickel, manganese having a cross-sectional dimension greater than 20 nanometers.
4. The high attenuation optical fiber according to claim 1, wherein the core layer contains 0 to 13mol% of aluminum element and/or 0 to 20mol% of germanium element in terms of mass percentage.
5. The high attenuation optical fiber according to claim 1, wherein the high attenuation optical fiber has an attenuation coefficient of more than 0.5dB/cm in a wavelength range of 1250nm to 1625 nm.
6. The high attenuation optical fiber of claim 1, wherein the attenuation spectrum of said attenuated optical fiber is flat within 10% of the band O, E, S, C, L for fiber optic communications.
7. The method for producing a high attenuation optical fiber according to any one of claims 1 to 6, comprising the steps of:
(1) mixing a first phase containing metal elements according to a formula ratio with a second phase taking loose quartz glass powder as a main component to prepare a uniform solid phase; wherein the first phase is a liquid and/or solid phase;
(2) preparing a solid transparent glass body by using the uniform solid phase obtained in the step (1) as a raw material;
(3) taking the solid transparent glass body obtained in the step (2) as an optical fiber preform core rod to prepare a high-attenuation optical fiber preform and drawing the high-attenuation optical fiber preform into the high-attenuation optical fiber of any one of claims 1 to 6.
8. The method of claim 7, wherein the first phase in step (1) is a liquid phase containing two or more of cobalt ions, iron ions, chromium ions, manganese ions, and nickel ions.
9. The method for preparing a high attenuation optical fiber according to claim 7, wherein the loose silica glass powder in the step (1) is prepared by a chemical vapor deposition process, and the density of the silica glass powder is 0.3-1.1 g/cm3。
10. The method for preparing a high attenuation optical fiber according to claim 7, wherein the loose silica glass powder in the step (1) contains 0 to 20mol% of germanium element.
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| GB8713081D0 (en) * | 1987-06-04 | 1987-07-08 | Pirelli General Plc | Optical fibre attenuators |
| US5572618A (en) * | 1994-07-13 | 1996-11-05 | Lucent Technologies Inc. | Optical attenuator |
| US6115524A (en) * | 1997-07-31 | 2000-09-05 | Corning Incorporated | Optical waveguide attenuating device and method for producing the same |
| KR20020064506A (en) * | 2001-02-02 | 2002-08-09 | (주)옵토네스트 | Gain equalizing optical-fiber for attenuator |
| EP1942083A1 (en) * | 2006-12-07 | 2008-07-09 | Datwyler Fiber Optics S.A. | Method and apparatus for fabricating a preform for an active optical fiber, active optical fiber and amplifier |
| CN102073093B (en) * | 2010-11-24 | 2012-10-17 | 烽火通信科技股份有限公司 | High-attenuation optical fiber and manufacturing method of same |
| CN102992613B (en) * | 2012-12-25 | 2015-09-30 | 长飞光纤光缆股份有限公司 | A kind of rare earth Uniform Doped optical fiber prefabricated rod mandrel and preparation method thereof |
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