Patent Description:
With the continuous development of modern communication technology, communication equipment used under special environmental conditions requires higher data transmission volume and transmission speed. In the fields of aerospace, nuclear power engineering, medical equipment, etc., due to the existence or use of radioactive sources/high-energy particle rays, strict requirements have been put forward for communication medium (especially optical fiber cable itself). In an irradiation condition, an irradiation ray that mainly threatens communication equipment and the communication optical fiber is a γ-ray. Free electrons and holes are generated from the quartz material of the main body of the optical fiber in the irradiation environment under the action of the γ-ray, and are captured by oppositely charged defect centers to form a "color center", which produces additional optical absorption peaks in multiple bands. The absorption peaks caused by radiation cause the attenuation of optical signals in the optical fiber to increase, and the absorption peaks near the communication band have a particularly significant impact on the attenuation of the optical fiber.

The optical fiber manufacturing process involves rapid switching of the temperature field of thousands of degrees Celsius, which will introduce a large number of material defects. These defects are the main source of the "color center" induced by radiation rays, so how to control the material defects in the optical fiber is the key to improve the radiation resistance of the optical fiber. Patent application <CIT> and patent application <CIT> disclose a method for improving radiation-resistance performance of an optical fiber through doping a fluorine element in the quartz material of an optical fiber. The fluorine element itself plays a role of "ring-opening" in a quartz glass network structure, which can reduce the number of Si-O five-membered rings and four-membered rings and transform into two-membered or three-membered ring structures. In combination with the characteristics of non-doped Ge element in the optical fiber, the number of the material defects can be reduced and the formation of the irradiated "color center" can be suppressed. However, this technical method requires the use of high-concentration fluorine doping technology, and the low solubility of the fluorine element in quartz matrix and the instability of the Si-O-F series products make this method relatively complex, which may require a modified chemical vapor deposition (MCVD) technology or a plasma-assisted chemical vapor deposition (PCVD) technology combined with advanced fluorine doping control technology to achieve. Similarly, due to the characteristics of the above-mentioned fluorine element, this method is severely limited in the preparation of the optical fiber with a higher numerical aperture. Patent application <CIT> discloses a method for improving radiation-resistance performance of an optical fiber by using a heat treatment technique and a pre-irradiation technique. The heat treatment technology, long-term heat preservation in a temperature zone near a glass fictive temperature, utilizes a thermal effect to eliminate the material defects in the quartz matrix so as to achieve the purpose of reducing the formation of the "color center". The pre-irradiation technique utilizes the effect of γ-rays and unstable lattice points in the optical fiber, although the inherent loss of the optical fiber will be slightly increased, the purpose of eliminating the material defects can also be achieved. This method is mainly applicable to the optical fiber with short length, while the longer optical fiber cannot use the method because it is difficult to ensure the strength of the optical fiber after removing the coating layer (polyacrylic acid-based coating layer is deformed and failed at a temperature higher than <NUM>). In the process of fiber drawing, this method requires a long thermal annealing time (> <NUM>), which is not consistent with the actual equipment conditions of the optical fiber industrial production (conventional fiber drawing speed ranges from <NUM>/min to <NUM>/min).

In view of the fact that the manufacturing of the existing radiation-resistant optical fiber requires the use of a complex deposition process and requires to manufacture a "pure silica core + fluorine-doped silica cladding" structure, which has a long manufacturing cycle and a complex process, and at the same time, the manufacturing process of the existing radiation-resistant optical fiber mainly involves the treatment for the optical fiber, which is difficult to ensure the strength of the optical fiber and does not consistent with the actual equipment conditions of the optical fiber industrial production, the current problem is the urgent need to research and develop a new method for manufacturing a radiation-resistant optical fiber.

<CIT> discloses a manufacturing method for a radiation-resistant optical fiber, comprising the following steps: irradiating electromagnetic waves to a perform for optical fibers and taking out of the preform for optical fibers to produce a glass defect; immersing the perform for optical fibers in the atmosphere which consists of hydrogen gas; irradiating electromagnetic waves again; drawing the preform for optical fibers so as to obtain the optical fibers for ultraviolet light transmission.

In view of the defects existing in the prior art, the purpose of the present invention is to provide a manufacturing method for a radiation-resistant optical fiber. The method of the present invention makes a prepared optical fiber have good radiation-resistance performance through sequentially performing annealing, hydrogen loading, and irradiation preprocessing on an optical fiber preform, which effectively solves the problem that the existing radiation-resistant optical fiber can only be manufactured through a vapor deposition process and a deep fluorine doping process. At the same time, the method of the present invention does not involve complex preform manufacturing equipment, the types of preforms are not limited, and the application range is wide.

To achieve the above purpose, the present invention provides a manufacturing method for a radiation-resistant optical fiber, comprising the following steps:.

The method of annealing comprises: heating the optical fiber preform to a setting temperature T<NUM> and holding the temperature T<NUM> for a period of time ti, then cooling down the optical fiber preform according to a fixed annealing rate K<NUM>, and natural cooling after reaching a target temperature T<NUM>, so as to manufacture an annealed optical fiber preform.

The setting temperature T<NUM> ranges from <NUM> to <NUM>, the holding time ti ranges from <NUM> to <NUM>, the annealing rate K<NUM> ranges from <NUM>/min to <NUM>/min, and the target temperature T<NUM> ranges from <NUM> to <NUM>.

On the basis of the above technical solution, the setting temperature T<NUM> ranges from <NUM> to <NUM>, the holding time ti ranges from <NUM> to <NUM>, the annealing rate K<NUM> ranges from <NUM>/min to <NUM>/min, and the target temperature T<NUM> ranges from <NUM> to <NUM>.

On the basis of the above technical solution, the method of hydrogen loading comprises: placing the annealed optical fiber preform in a hydrogen atmosphere for performing the hydrogen loading processing, so as to manufacture a hydrogen-loaded optical fiber preform.

On the basis of the above technical solution, the pressure of the hydrogen ranges from <NUM>. 5MPa to <NUM>. 0MPa, the concentration of the hydrogen is greater than 99v%, and the time for the hydrogen loading processing ranges from <NUM> to <NUM>.

On the basis of the above technical solution, the pressure of the hydrogen ranges from <NUM>. 8MPa to <NUM>. 5MPa, the concentration of the hydrogen is greater than 99v%, and the time for the hydrogen loading processing ranges from <NUM> to <NUM>.

On the basis of the above technical solution, the method of irradiation comprises: using a γ-ray source to perform the irradiation processing on the hydrogen-loaded optical fiber preform, so as to manufacture a irradiated optical fiber preform.

On the basis of the above technical solution, the irradiation processing is performed under the conditions of a radiation dose rate of 10Gy/h-200Gy/h and a total radiation dose of <NUM>. 4kGy-<NUM>.

On the basis of the above technical solution, in an environment where the total radiation dose is 10Gy, the attenuation of the single mode optical fiber both at <NUM> wave band and at <NUM> wave band does not exceed <NUM>. 5dB/km; and the attenuation of the multimode optical fiber at <NUM> wave band does not exceed <NUM>. 6dB/km; in an environment where the total radiation dose is 10kGy, the attenuation of the single mode optical fiber both at <NUM> wave band and at <NUM> wave band does not exceed <NUM>. 0dB/<NUM>; and the attenuation of the multimode optical fiber at <NUM> wave band does not exceed <NUM>.

Compared with the prior art, the present invention has the following advantages:.

For easier understanding, the present invention will be further described below in detail with reference to the drawings in combination with the embodiments. It should be understood that these embodiments are illustrative only and are not intended to limit the present invention.

In order to facilitate understanding of the present invention, first technical terms involved in the present invention are defined as follows.

The term "single mode optical fiber" refers to an optical fiber that only transmits one mode of optical signal within an optical fiber core.

The term "multimode optical fiber" refers to an optical fiber that simultaneously transmits multiple modes of optical signals within an optical fiber core.

The single mode optical fibers involved in the present invention are a G. <NUM> optical fiber (non-dispersion shifted single mode optical fiber), a G. <NUM> optical fiber (cut-off wavelength shifted single mode optical fiber), a G. <NUM> optical fiber (non-zero dispersion shifted single mode optical fiber) and a G. <NUM> optical fiber (bending-insensitive single mode optical fiber) defined by the International Telecommunication Union Telecommunications Standards Branch (ITU-T).

The multimode optical fibers involved in the present invention are A1a and A1b multimode fibers defined by the International Electrotechnical Commission (IEC), which are respectively referred to as <NUM>/<NUM> multimode fibers (a multimode fiber with a core diameter of <NUM> and a cladding diameter of <NUM>) and <NUM>/<NUM> multimode fiber (a multimode fiber with a core diameter of <NUM> and a cladding diameter of <NUM>).

As mentioned above, the manufacturing of existing radiation-resistant optical fiber requires a complex deposition process and requires to manufacture a structure of "pure silica (quartz) core + fluorine-doped silica (quartz) cladding", which has a long manufacturing cycle and a complex process; at the same time, the manufacturing process of existing radiation-resistant optical fiber mainly involves the handling of the optical fiber, which is difficult to ensure the strength of the optical fiber and does not conform to the actual equipment conditions of the optical fiber industrial production. The inventor of the present invention has conducted a large number of experimental studies in the field of a radiation-resistant optical fiber manufacturing and found that the method of sequentially performing annealing, hydrogen loading and irradiation preprocessing on an optical fiber preform, and then performing drawing thereon, can effectively improve the radiation-resistance performance of the manufactured optical fiber, and the manufacturing method is not limited by the types of the optical fiber preforms and can manufacture the radiation-resistant optical fiber simply, rapidly and on a mass scale.

Therefore, the embodiment of the present invention provides a manufacturing method for a radiation-resistant optical fiber, comprising the following steps:.

The optical fiber preform to be processed in the method of the present invention is a commercial optical fiber preform, the main component of which is optical fiber-grade high-purity SiO<NUM> glass. It is easy to understand that in order to meet the requirements of the waveguide structure and the optical fiber performance, the core and the cladding material of the optical fiber preform used in the present invention may further comprise a certain concentration of doping elements, such as Ge, F, P, B or Al.

The diameter of the optical fiber preform used in the method of the present invention ranges from <NUM> to <NUM> and the length ranges from <NUM> to <NUM>. The manufacturing process of the commercial optical fiber preform can be MCVD, PCVD, OVD or VAD. The commercial optical fiber preform can be either a single mode optical fiber preform or a multimode optical fiber preform.

The annealing method in step S1 of the present invention comprises: heating the optical fiber preform to a setting temperature T<NUM> and holding the temperature T<NUM> for a period of time ti, then cooling down the optical fiber preform according to a fixed annealing rate K<NUM>, and natural cooling after reaching a target temperature T<NUM>, so as to obtain an annealed optical fiber preform.

In the present invention the setting temperature T<NUM> ranges from <NUM> to <NUM>, the holding time ti ranges from <NUM> to <NUM>, the annealing rate K<NUM> ranges from <NUM>/min to <NUM>/min, and the target temperature T<NUM> ranges from <NUM> to <NUM>.

Preferably, the setting temperature T<NUM> ranges from <NUM> to <NUM>, the holding time ti ranges from <NUM> to <NUM>, the annealing rate K<NUM> ranges from <NUM>/min to <NUM>/min, and the target temperature T<NUM> ranges from <NUM> to <NUM>.

The annealing method of the present invention can adjust hypothetical temperature of quartz glass to change microstructure relaxation, so as to eliminate internal stress of quartz.

The inventor of the present invention has found that the conditions of annealing processing may affect the radiation-resistance performance of the resulting optical fiber. In the three steps of the annealing process, i.e., temperature rise/thermal insulation - annealing - cooling, the annealing is different from the thermal insulation, which cools down at a slower rate. Annealing equipment with poor temperature control accuracy (e.g., cooling rate of <NUM>/min) will affect the annealing effect of the optical fiber preform, thereby eventually affecting the radiation-resistance performance of the resulting optical fiber.

The hydrogen loading method in step S2 of the present invention comprises: placing the annealed optical fiber preform in a hydrogen atmosphere for performing the hydrogen loading processing, so as to obtain a hydrogen-loaded optical fiber preform.

Preferably, the pressure of the hydrogen ranges from <NUM>. 5MPa to <NUM>. 0MPa, the concentration of the hydrogen is greater than 99v%, and the time for the hydrogen loading processing ranges from <NUM> to <NUM>.

Further preferably, the pressure of the hydrogen ranges from <NUM>. 8MPa to <NUM>. 5MPa, the concentration of the hydrogen is greater than 99v%, and the time for the hydrogen loading processing ranges from <NUM> to <NUM>.

The hydrogen loading method of the present invention can make hydrogen molecules enter the quartz glass structure in the form of Si-OH, although the Si-OH itself will increase the absorption of the optical fiber at <NUM> window, material defects such as non-bridging oxygen oxygen vacancies can be eliminated with a small amount of H entering SiO<NUM> network structure, which enhances the radiation-resistance level of the optical fiber.

The irradiation method in step S3 of the present invention comprises: using a γ-ray source to perform the irradiation processing on the hydrogen-loaded optical fiber preform, so as to obtain a irradiated optical fiber preform.

Preferably, the irradiation processing is performed under the conditions of a radiation dose rate of 10Gy/h-200Gy/h and a total radiation dose of <NUM>. 4kGy-<NUM>.

Further preferably, the irradiation processing is performed under the conditions of a radiation dose rate of 10Gy/h-100Gy/h and a total radiation dose of <NUM>. 5kGy-<NUM>.

The inventor of the present invention has found that in general, a higher radiation dose rate will cause irreversible material defects in the quartz matrix of the preform, and the absorption caused by these defects cannot be recovered even if the radiation source is removed. The environment where the radiation-resistant optical fibers are used is mostly long-term service conditions (<NUM>. The initial attenuation of the optical fiber must be strictly controlled when manufacturing the radiation-resistant optical fibers, therefore, the preform should not receive the radiation with an excessively high dose rate. On the other hand, the total radiation dose of the preform is positively related to the volume of the preform. The larger the preform, the greater the total radiation dose. Therefore, the irradiation method of the present invention further needs to strictly control the radiation dose rate of the optical fiber preform while controlling the total radiation dose of the optical fiber preform.

In step S4 of the present invention, a conventional method in the prior art can be used to draw the irradiated optical fiber preform into a radiation-resistant single mode optical fiber or a radiation-resistant multimode optical fiber.

The radiation-resistant optical fiber manufactured by the present invention has the following characteristics: in an environment where the total radiation dose is 10Gy, the attenuation of the single mode optical fiber both at <NUM> wave band and at <NUM> wave band does not exceed <NUM>. 5dB/km; and the attenuation of the multimode optical fiber at <NUM> wave band does not exceed <NUM>. 6dB/km; in an environment where the total radiation dose is 10kGy, the attenuation of the single mode optical fiber both at <NUM> wave band and at <NUM> wave band does not exceed <NUM>. 0dB/<NUM>; and the attenuation of the multimode optical fiber at <NUM> wave band does not exceed <NUM>.

The present invention will be further described below in detail with reference to the drawings in combination with the embodiments.

A clean and complete commercial single mode optical fiber preform with a length of <NUM> and a diameter of <NUM> is chosen, and then placed in a box type resistance furnace. First, heating the optical fiber preform to a setting temperature T<NUM> = <NUM>, after holding the temperature for a period time ti = <NUM>, cooling down the optical fiber preform to a target temperature T<NUM>=<NUM> at an annealing rate K<NUM> = <NUM>/min. Then stopping heating the preform and naturally cooling it along with the furnace. The cooled optical fiber preform is placed in a hydrogen pressure tank with a hydrogen pressure of <NUM>. 0MPa, a hydrogen concentration of greater than 99v% and a hydrogen loading time of <NUM>. After the hydrogen loading, the optical fiber preform is placed in an irradiation facility at room temperature and air environment for performing a γ-ray irradiation. The radiation dose rate is 50Gy/h and the total radiation dose is <NUM>. After finishing the above preprocessing to the optical fiber preform, the single mode optical fiber preform is finally drawn into a G. <NUM> single mode optical fiber according to a conventional drawing process. The specific process and optical fiber indicators are shown in Table <NUM>.

A clean and complete commercial single mode optical fiber preform with a length of <NUM> and a diameter of <NUM> is chosen, and then placed in a box type resistance furnace. First, heating the optical fiber preform to a setting temperature T<NUM> = <NUM>, after holding the temperature for a period time ti = <NUM>, cooling down the optical fiber preform to a target temperature T<NUM>=<NUM> at an annealing rate K<NUM> = <NUM>/min. Then stopping heating the preform and naturally cooling it along with the furnace. The cooled optical fiber preform is placed in a hydrogen pressure tank with a hydrogen pressure of <NUM>. 5MPa, a hydrogen concentration of greater than 99v% and a hydrogen loading time of <NUM>. After the hydrogen loading, the optical fiber preform is placed in an irradiation facility at room temperature and air environment for performing a γ-ray irradiation. The radiation dose rate is 85Gy/h and the total radiation dose is <NUM>. After finishing the above preprocessing to the optical fiber preform, the single mode optical fiber preform is finally drawn into a G. <NUM> single mode optical fiber according to a conventional drawing process. The specific process and optical fiber indicators are shown in Table <NUM>.

A clean and complete commercial single mode optical fiber preform with a length of <NUM> and a diameter of <NUM> is chosen, and then placed in a box type resistance furnace. First, heating the optical fiber preform to a setting temperature T<NUM> = <NUM>, after holding the temperature for a period time ti = <NUM>, cooling down the optical fiber preform to a target temperature T<NUM>=<NUM> at an annealing rate K<NUM> = <NUM>/min. Then stopping heating the preform and naturally cooling it along with the furnace. The cooled optical fiber preform is placed in a hydrogen pressure tank with a hydrogen pressure of <NUM>. 8MPa, a hydrogen concentration of greater than 99v% and a hydrogen loading time of <NUM>. After the hydrogen loading, the optical fiber preform is placed in an irradiation facility at room temperature and air environment for performing a γ-ray irradiation. The radiation dose rate is 70Gy/h and the total radiation dose is <NUM>. After finishing the above preprocessing to the optical fiber preform, the single mode optical fiber preform is finally drawn into a G. <NUM> single mode optical fiber according to a conventional drawing process. The specific process and optical fiber indicators are shown in Table <NUM>.

A clean and complete commercial single mode optical fiber preform with a length of <NUM> and a diameter of <NUM> is chosen, and then placed in a box type resistance furnace. First, heating the optical fiber preform to a setting temperature T<NUM> = <NUM>, after holding the temperature for a period time ti = <NUM>, cooling down the optical fiber preform to a target temperature T<NUM>=<NUM> at an annealing rate K<NUM> = <NUM>/min. Then stopping heating the preform and naturally cooling it along with the furnace. The cooled optical fiber preform is placed in a hydrogen pressure tank with a hydrogen pressure of <NUM>. 0MPa, a hydrogen concentration of greater than 99v% and a hydrogen loading time of <NUM>. After the hydrogen loading, the optical fiber preform is placed in an irradiation facility at room temperature and air environment for performing a γ-ray irradiation. The radiation dose rate is 50Gy/h and the total radiation dose is <NUM>. After finishing the above preprocessing to the optical fiber preform, the single mode optical fiber preform is finally drawn into a G. <NUM> single mode optical fiber according to a conventional drawing process. The specific process and optical fiber indicators are shown in Table <NUM>.

A clean and complete commercial <NUM>/<NUM> multimode optical fiber preform with a length of <NUM> and a diameter of <NUM> is chosen, and then placed in a box type resistance furnace. First, heating the optical fiber preform to a setting temperature T<NUM> = <NUM>, after holding the temperature for a period time ti = <NUM>, cooling down the optical fiber preform to a target temperature T<NUM>=<NUM> at an annealing rate K<NUM> = <NUM>/min. Then stopping heating the preform and naturally cooling it along with the furnace. The cooled optical fiber preform is placed in a hydrogen pressure tank with a hydrogen pressure of <NUM>. 66MPa, a hydrogen concentration of greater than 99v% and a hydrogen loading time of <NUM>. After the hydrogen loading, the optical fiber preform is placed in an irradiation facility at room temperature and air environment for performing a γ-ray irradiation. The radiation dose rate is 33Gy/h and the total radiation dose is <NUM>. After finishing the above preprocessing to the optical fiber preform, the multimode optical fiber preform is finally drawn into a <NUM>/<NUM> multimode optical fiber according to a conventional drawing process. The specific process and optical fiber indicators are shown in Table <NUM>.

A clean and complete commercial <NUM>/<NUM> multimode optical fiber preform with a length of <NUM> and a diameter of <NUM> is chosen, and then placed in a box type resistance furnace. First, heating the optical fiber preform to a setting temperature T<NUM> = <NUM>, after holding the temperature for a period time ti = <NUM>, cooling down the optical fiber preform to a target temperature T<NUM>=<NUM> at an annealing rate K<NUM> = <NUM>/min. Then stopping heating the preform and naturally cooling it along with the furnace. The cooled optical fiber preform is placed in a hydrogen pressure tank with a hydrogen pressure of <NUM>. 78MPa, a hydrogen concentration of greater than 99v% and a hydrogen loading time of <NUM>. After the hydrogen loading, the optical fiber preform is placed in an irradiation facility at room temperature and air environment for performing a γ-ray irradiation. The radiation dose rate is 14Gy/h and the total radiation dose is <NUM>. After finishing the above preprocessing to the optical fiber preform, the multimode optical fiber preform is finally drawn into a <NUM>/<NUM> multimode optical fiber according to a conventional drawing process. The specific process and optical fiber indicators are shown in Table <NUM>. For comparison purposes, the attenuation results of the optical fibers of the existing radiation-resistant single mode optical fiber (available from FUJIKURA) and radiation-resistant multimode optical fiber (available from Draka) after 10Gy and 10kGy dose radiation are respectively shown in Table <NUM> below.

By comparing the data in Table <NUM> and Table <NUM>, it can be seen that the optical fiber attenuation of the radiation-resistant optical fiber provided by the present invention after 10Gy dose radiation and 10kGy dose radiation is smaller than that of the existing radiation-resistant optical fiber. Therefore, the radiation-resistant optical fiber provided by the present invention has good radiation-resistant performance.

Claim 1:
A manufacturing method for a radiation-resistant optical fiber, comprising the following steps:
sequentially performing annealing, hydrogen loading, and irradiation preprocessing on an optical fiber preform; and
performing drawing on the preprocessed optical fiber preform, so as to manufacture a radiation-resistant single mode optical fiber or a radiation-resistant multimode optical fiber;
wherein the method of annealing comprises: heating the optical fiber preform to a setting temperature T<NUM> and holding the temperature T<NUM> for a period of time ti, then cooling down the optical fiber preform according to a fixed annealing rate K<NUM>, and natural cooling after reaching a target temperature T<NUM>, so as to manufacture an annealed optical fiber preform;
wherein the setting temperature T<NUM> ranges from <NUM> to <NUM>, the holding time ti ranges from <NUM> to <NUM>, the annealing rate K<NUM> ranges from <NUM>/min to <NUM>/min, and the target temperature T<NUM> ranges from <NUM> to <NUM>.