Radiation-resistant fibre-optic guide, method for production thereof and method of improving radiation resistance of fibre-optic guide (versions)

FIELD: physics.

SUBSTANCE: fibre-optic guide is obtained by chemical deposition of quartz glass from a mixture of starting gaseous reagents. The optic guide has a core of undoped quartz glass with low content of chlorine in the glass of the core due to considerable excess of oxygen O2 relative to silicon tetrachloride SiCl4 during manufacture.

EFFECT: providing high radiation resistance of an optic guide in the near infrared range by suppressing radiation-induced light absorption.

32 cl, 7 dwg

 

The technical field

The invention relates to the field of optical fibers, resistant to nuclear and/or ionizing radiation, and is industrially applicable in systems fiber-optic communication intended for use in the exposure to the above-mentioned radiation (inside and in the vicinity of nuclear power facilities, nuclear facilities with danger, satellites, weapons, military and special machinery, and others).

Prior art

In the prior art it is known that the most popular type of fiber is a fiber optical fibers based on silica glass (i.e., having a core and a shell made of doped or undoped silica glass) and is single-mode at the operating wavelength λ0in the near-infrared (IR) range, which below will be defined as the wavelength interval 0,78...of 1.9 microns.

Today from near-IR to optical communication is used spectral range ~1,29...1,69 μm and first of all the most used wavelengths of 1.31 and 1.55 μm (see E. Desurvire "Optical Communication in 2025", 31stEuropean Conference on Optical Communication, ECOC-2005, Glasgow, UK, 25-29 September 2005, paper Mo 2.1.3). Modern the most important applications of such optical fibers are optical communication system including the Internet (see E. M. Dianov, "On the threshold of pet-era". The us is EHE physical Sciences, volume 183, No. 5, S. 511-518 (2013)).

Blanks for such fibers made by the method of chemical deposition of quartz glass from a mixture of a source of gaseous reagents. Developed and well-known processes, implement this method: MCVD, FCVD, VAD, OVD, PCVD and SPCVD. They are described, for example, in the following scientific articles: S. R. Nagel, J. B. MacChesney, K. L. Walker, "An overview of the modified chemical vapor deposition (MCVD) process and performance" IEEE Journal of Quantum Electronics, vol.18, No.4, pp.459-476 (1982); A. A. Malinin, A. S. Zlenko, U. G. Akhmetshin, S. L. Semjonov "Furnace chemical vapor deposition (FCVD) method for special optical fibers fabrication", Proc. SPIE, vol. 7934, Paper 793418 (2011); K. Okamoto, T. Edahiro, M. Nakahara "Transmission characteristics of VAD multimode optical fibers". Applied Optics, vol.20, pp.2314-2318 (1981); M. G. Blankenship, C. W. Deneka "The outside vapor deposition method of fabricating optical waveguide fibers", IEEE Transactions on Wicrowave Theory and Techniques, vol.30, pp.1406-1411 (1982); Th. Hunlich, H. Bauch, R. Th. Kersten, V. Paquet, G. F. Weidmann "Fiber perform fabrication using plasma technology", Journal of Optical Communication, vol.4, pp.122-129 (1987); E. M. Dianov, K. M. Golant, A. S. Kurkov, R. R. Khrapko, A. L. Tomashuk "Low-hydrogen silicon oxynitride optical fibres prepared by SPCVD", Journal of Lightwave Technology, vol.13, pp.1471-1474 (1995). After that, the fiber light guides are made of billet-known method of drawing. In the process of pulling on the fiber light guide is applied protective coating. In the fiber, the fiber consists of a core and a shell based on quartz glass and a protective coating.

The most important characteristic of single-mode fiber is wavelength attack the first high fashion λ with. The fiber is single-mode at wavelength λ0if λ0c. (see F. Krahn, B. Sange, E.-G. Neumann, H. Schwierz, J. Streckert, F. Wilczewski "Cutoff wavelength of single-mode fibers: definition, measurement, and length and curvature dependence". Fiber and Integrated Optics, vol.8, pp.203-215 (1989)).

In some applications of fiber lightguides in the operation are placed in the fields of nuclear and/or ionizing radiation, or may be under the influence of such radiation during operation. Nuclear radiation refers to fast neutrons, protons and beta radiation; ionizing radiation - gamma rays, x-rays, ultraviolet radiation (UV) and visible ranges, which can fall on the optic fiber from the outside or distributed inside of the fibre.

It is known that applications of optical fibers in the exposure to nuclear and/or ionizing radiation, there is a problem of increasing the optical loss in the optical fiber until the loss of transparency of the fibre. This phenomenon is known as radiation-induced absorption (RNP) light in an optical fiber (see B. Brichard, A. Fernandez Fernandez, H. Ooms, F. Berghmans, M. Decreton, A. Tomashuk, S. Klyamkin, M. Zabezhailov, I. Nikolin, V. Bogatyrjov, E. Hodgson. T. Kakuta, T. Shikama, T. Nishitani, A. Costley, G. Vayakis "Radiation-hardening techniques of dedicated optical fibres used in plasma diagnostic systems in ITER", Journal of Nuclear Materials, vol.329-333, pp.1456-1460 (2004)). The effect of RNP attributed to aetsa fact, the above radiation breaks the chemical bonds in the grid glass of the fibre, resulting in a grid of glass are formed radiation color centers (RPC) that absorb light propagating through the fiber to the fiber (see D. L. Griscom, K. M. Golant, A. L. Tomashuk, D. V. Pavlov, Yu.A. Tarabrin "Gamma-radiation resistance of aluminum-coated all-silica optical fibers fabricated using different types of silica in the core", Applied Physics Letters, vol.69 (3), pp.322-324 (1996)).

Optic fibers for optical communication, which is widely used outside the field of nuclear and/or ionizing radiation, have a core made of quartz glass doped oxide, Germany. At the same time, it is on the atoms Germany in the grid quartz glass occurs a large number of the RPC, which gives unacceptably large RNP in the near infrared range, making such fiber lightguides do not possess property of radiation resistance.

The prior art fiber optical fiber with increased radiation resistance, which instead of a core made of quartz glass doped oxide, Germany, is the core of undoped silica glass (see G. Tanaka, M. Watanabe, K. Yano "Characteristics of pure silica core single-mode fiber", Fiber and Integrated Optics, vol.7, pp.47-56 (1987)). The increase in radiation resistance of this fiber-optic waveguides is connected with the exception of the glass composition of atoms Germany, creating a large number of the RPC.

The disadvantage of the fibers of the second fiber is a low radiation resistance, due to three mechanisms RNP affecting the spread of the light signal in the near infrared range, the suppression of which would increase the radiation resistance of the optical fiber in this spectral region. These three mechanisms RNP following:

is primarily RNP caused the RPC associated with chlorine atoms, which are in mesh nominally undoped quartz glass in the synthesis of glass blanks from a mixture of a source of gaseous reactants, usually containing molecular oxygen O2and silicon tetrachloride SiCl4. This RPP increases with increasing chlorine content of the glass fiber. It reaches its maximum in the UV range and monotonically decreases with increasing wavelength, and manifesting in the near infrared range (see S. Girard, C. Marcandella, A. Alessi, A. Boukenter, Y. Ouerdane, N. Richard, P. Paillet, M. Gaillardin, M. Raine "Transient radiation responses of optical Fibers: influence of MCVD process parameters", IEEE Transactions on Nuclear Science, vol.59, No 6, pp.2894-2901 (2012)). In the irradiation process of the fibre of nuclear and/or ionizing radiation is RNP increases monotonically with increasing dose (see D. L. Griscom, K. M. Golant, A. L. Tomashuk, D. V. Pavlov, Yu.A. Tarabrin "Gamma-radiation resistance of aluminum-coated all-silica optical fibers fabricated using different types of silica in the core", Applied Physics Letters, vol.69 (3), pp.322-324 (1996)). In the future it RNP will be referred to as RNP-1";

the second mechanism is PPR, not associated with chlorine atoms. It also has a maximum in the visible and UV range of the spectrum and monotonically decreases with increasing wavelength. At high dose of ionizing radiation is RNP depends on the dose nonmonotonic: it increases sharply at the beginning of the irradiation, and then decreases with increasing dose (see A. L. Tomashuk, K. M. Golant "Radiation-resistant and radiation-sensitive silica optical fibers", Proceeding of SPIE, vol.4083, pp.188-201 (2000)). The nature of the RPC responsible for this PPR, is unknown and still not theoretically explained. In the future it RNP will be referred to as RNP-2";

the third mechanism is PPR, peaking at a wavelength of about 1.9 μm and a monotonically decreasing with decreasing wavelength (see E. Reginer, I. Flammer, S. Girard, F. Gooijer, F. Actten, G. Kuyt "Low-dose radiation-induced attenuation at infrared wavelengths for P-doped, Ge-doped and pure silica-core optical fibers", IEEE Transactions on Nuclear Science, vol.54, No 4, pp.1115-1119 (2007)). The nature of the RPC responsible for this PPR, also not known. In the future it RNP will be called "PPR-3".

One of the promising directions of development of radiation-resistant fiber is the manufacture of their components made of quartz glass doped with fluorine.

As a fairly close analogue of the proposed fiber-known radiation-resistant fiber optical fiber with a core of undoped quartz glass KS-4V and a shell made of silica glass doped with fluorine (see V. A. Bogatyrjov, I. Cheremisin, E. M. Dianov, K. M. Golant, A. L. Tomashuk "Super-high-strength metal-coated low-hydroxyl low-chlorine all-silica optical fibers", IEEE Transactions on Nuclear Science, vol.43,No.3, pp.1057-1060 (1996)). The high radiation resistance of the optical fiber due to the low content of impurities chloride (0,002 weight percent), which suppressed RNP-1. Also suppressed RNP-3. Quartz glass KS-4V produced in the form of three-dimensional blocks, and for the manufacture of wood fiber-optic waveguides from the block machined rod, which precipitated reflective shell made of silica glass doped with fluorine.

The disadvantage of this close analogue is that the fiber is single-mode in the near infrared range, as it is almost impossible to drill a fairly thin homogeneous rod (diameter less than 1 mm) for use as the core of the billet single-mode fiber. Also a disadvantage is the fact that this fiber is present RNP-2.

Foreign patent publications known radiation-resistant fiber of the optical fiber based on silica glass and method of manufacturing, including the manufacturing of the workpiece containing the core and shell, which are synthesized by the method of chemical deposition of quartz glass from a mixture of a source of gaseous reactants, and the subsequent stretching of the fibre from the preform (see U.S. patent 7440673 B2 "RADIATION RESISTANT SINGLE-MODE OPTICAL FIBER AND METHOD OF MANUFACTURING THEREOF", publ. 21.10.2008, IPC G02B 6/00). When the manufacturer for whom otoki quartz glass core alloyed with fluorine, so its refractive index becomes 0,1...0,3% less than the refractive index of undoped quartz glass, and quartz glass shell legarrette even larger amount of fluorine, so that its refractive index becomes less than the core refractive index 0.3...0.5 percent. The point is that when doped quartz glass with fluorine in the synthesis process of the glass workpiece is suppressed occurrence in mesh glass of chlorine atoms (atoms more reactive fluorine substituted chlorine atoms). Therefore, because of the small amount of chlorine in the grid of the glass core is minimized RNP-1. In addition, in the optical fiber due to the presence of fluorine in the glass suppressed RNP-3. Therefore, the fiber has a high radiation resistance.

The disadvantage of this method of manufacturing a radiation-resistant optical fiber is the complexity of its implementation, since the production of billet requires consistent application of two technologies: first technology VAD for the synthesis of the glass core, and then OVD technology for the synthesis of the glass shell. In addition, the disadvantage of this radiation-resistant optical fiber and method of its manufacture is the fact that RNP-2 in an optical fiber is suppressed not fully.

Closer to the method of manufacturing the inventive fiber can be recognized as the method of manufacturing adiciona-resistant fiber of the optical fiber based on silica glass, doped with fluorine presented in the descriptions of U.S. patents 7689093 B2 Fluorine-Doped Optical Fiber", publ. 30.03.2010, IPC G02B 6/00, G02B 6/02 and 7526177 B2 Fluorine-Doped Optical Fiber", publ. 28.04.2009, IPC G02B 6/00; G02B 6/036, based on the total priority application FR 20060006058 from 04.07.2006. The method includes the manufacturing of the workpiece containing the core and shell, which are synthesized in a single (not double, as in previous similar) process of chemical deposition of quartz glass from a mixture of a source of gaseous reactants, and the extraction of the fibre from the preform. In this way the core and the cladding is also synthesized from silica glass doped with fluorine, and the core refractive index more than 1.5·10-3below the refractive index of undoped quartz glass, the refractive index of the shell more than 4.5·10-3below the refractive index of undoped quartz glass, and the difference of the refractive indices of the core and the shell is not less than 3·10-3. The mixture of the source gas contains reagents reagents to synthesize quartz glass doped with fluorine. A preferred variant of the method is chemical precipitation of quartz glass on the inner surface of the support tube made of quartz glass (PCVD process). When the glass support traviscannabis outer sheath of the fiber, while the inner shell is formed of chemically precipitated glass. The essence of the method is the same as the previous analogue: when doped quartz glass with fluorine in the synthesis process of the glass workpiece is suppressed occurrence in mesh glass of chlorine atoms (atoms more reactive fluorine substituted chlorine atoms), so because of the small amount of chlorine in the grid of the glass core is minimized RNP-1. In addition, in the optical fiber due to the presence of fluorine in the glass suppressed RNP-3. In the fiber, the fiber has a high radiation resistance.

The disadvantage of this close analogue is the fact that the admixture of fluorine in the core reduces its refractive index, which in the presence of the outer shell worse svetovidovi properties of the fibre compared with the optical fiber, whose core is made of undoped quartz glass. In particular, in such an optical fiber with a core made of quartz glass doped with fluorine, can arise optical loss when it comes to bending. Another disadvantage is the fact that RNP-2 in the fiber with a core and a shell made of silica glass doped with fluorine, not fully suppressed.

With regard to the unique method of improving the radiation resistance of the fibre, from foreign Pat is the shaft publications known method of improving the radiation resistance of the fibre on the basis of the quartz glass core of undoped quartz glass, consisting in the fact that the fiber light guide is saturated with molecular hydrogen and irradiated with gamma radiation (U.S. patent 5267343 "Enhanced radiation resistant fiber optics", publ. 30.11.1993,, IPC G02B 6/00, G02B 6/02, C03C 25/60; C03C 25/62). The essence of the method is that in the process of gamma irradiation hydrogen atoms are in mesh glass in the place of the predecessors of the RPC (irregular chemical bonds in the grid glass, which arise the RPC under the action of radiation) and thereby suppress them. After gamma-irradiation of the fibre in the presence of hydrogen molecules mesh glass no longer contains the precursors of the RPC responsible for RNP-1 and RNP-2. Therefore, the fiber light guide becomes the property of high radiation resistance.

The disadvantage of this method is that its application has not suppressed predecessors RNP-3. Also the disadvantage of this method is the fact that in its application due to the absorption of hydroxyl groups OH, occur in the grid glass of the fibre due to the presence of hydrogen increases the optical loss in the near infrared range. Therefore, this method is effective for optical fibres, used only in the visible spectral range, but is not applicable for fiber optic cable designed for use in the near IR range.

Also known closer way to increase radiationresistant of the fibre, containing a core and a shell based on quartz glass and sealed protective coating applied over the membrane, and containing hydrogen and/or deuterium in high concentrations, providing increased radiation resistance of the fibre, and a method of manufacturing such a fiber-optic waveguides, including pulling the fiber from the preform, drawing on him in the process of pulling sealed cover and then place in a gas atmosphere of hydrogen and/or deuterium at high pressures and temperatures (see RF patent №2222032 "FIBER light guide (OPTIONS) AND METHOD thereof", publ. 27.04.2002,, IPC G02B 6/16, C03C 25/60, C03B 37/01). The essence of the invention that the hydrogen molecule H2and/or deuterium (D2diffuse through tight coating in the glass of the fibre and for a long time remain in the glass of the fibre after it is removed from the gas atmosphere. When optic fiber is exposed to ionizing and/or nuclear radiation the atoms of hydrogen and/or deuterium are in mesh glass fiber light guide in places torn apart by radiation chemical bonds, thereby eliminating the RPC responsible for RNP-1 and RNP-2. Therefore, the fiber light guide has the property of high radiation resistance.

The disadvantage of this JV is soba increase the radiation resistance is what fiber does not decrease RNP-3. Also the disadvantage of this method is the fact that because of the absorption of hydroxyl groups OH and/or OD-groups arising, respectively, from molecules of hydrogen (H2and deuterium D2in the grid glass under the influence of radiation, increased optical loss in an optical fiber in the near infrared range. Therefore, this method is effective to increase the radiation resistance of optical fibers that are used only in the visible spectral range, but is not applicable for the radiation resistance of optical fibers intended for use in the near IR range.

Disclosure of inventions

The task of the invention was to be radiation-resistant fiber of the optical fiber, method of manufacturing and method of improving the radiation resistance of the fibre has overcome these disadvantages of the known related analogues, namely largely suppressed at the same time all three mechanisms RNAs and thereby increased radiation resistance of the fibre in the near infrared range. It was also necessary to eliminate the above and other drawbacks.

The technical effect is achieved by the fact that one of the features of the proposed radiation resistant single-mode fiber light the gadfly with a core of undoped quartz glass, received with a considerable excess of oxygen, is the low content of chlorine in the glass core. The authors experimentally established that the proposed fiber suppressed all three mechanisms RNP and therefore provided a higher radiation resistance than that of the fiber similar. However, a considerable excess molar flow O2over SiCl4in a mixture of a source of gaseous reagents in the synthesis of the glass core is the only possible method of manufacturing such a fiber-optic waveguides. Removed and another significant disadvantage of the fiber similar: proposed radiation-resistant optical fiber is single-mode in the near infrared range, and the light-similar to no.

The authors of the present invention it is found experimentally that the cost optimization of reagents in the synthesis of the glass core preform according to the method of chemical deposition of quartz glass from a mixture of a source of gaseous reagents, namely, providing significant excess molar flow rate of molecular oxygen O2over the molar flow rate of silicon tetrachloride SiCl4possible to create a blank single-mode optical fiber with a core of undoped quartz glass, in which a reduced chlorine content, and therefore, in the optical fiber is suppressed RNP-1. She is also experimentally determined, what is suppressed, and all other mechanisms RNP (RNP-2 and RNP-3). Thus, with this method of manufacturing is provided by the high radiation resistance of the fibre, and due to the fact that the core is made of undoped quartz glass, i.e. does not contain fluorine, does not deteriorate svetovidovi properties of the fiber, in contrast to manufacturing methods, which are analogues.

The authors experimentally found that the way to increase the radiation resistance of optical fiber, consisting in the fact that during the synthesis of the core preform of the optical fiber is supported by a considerable excess molar flow rate of molecular oxygen O2over the molar flow rate of silicon tetrachloride SiCl4that applies to optical fibers with non-alloy core and core doped with fluorine. In contrast to the process, along with the suppression of all known mechanisms of ANP in the near infrared range and therefore ensuring a higher radiation resistance, the proposed method of increasing the radiation resistance and eliminates another disadvantage analogues, namely: in the application of the proposed method not having the optical loss in the optical fiber in the near IR range, caused by the absorption of OH - and OD-groups in the grid window.

Also, the authors found that radiation resistance depends on techno is logicheskih modes of synthesis of membrane preparation. To improve the radiation resistance of the fiber is necessary to synthesize region of the shell adjacent to the core, normal (direct) deposition of silica glass doped with fluorine when filing in the original mixture of SiCl4, SiF4and O2. When this is achieved a small value of the difference of the refractive indices of the core and the shell (not more than 0,006). Therefore, to improve svetovidovi properties of the fiber in the peripheral region of the membrane should get a very low refractive index (the difference of the refractive index with the core more than 0,007). For this region of the shell should be beset by impregnation of a porous layer of SiO2the silicon tetrafluoride. Importantly, in the present method of manufacture of the fibre to ensure a high radiation resistance does not require the introduction of fluorine into the core, and therefore, accordingly, are not allowed deterioration svetovidovi properties of the inventive fiber.

Thus, according to the first independent claim (aspect) of the invention provides a radiation-resistant fiber fiber containing a core and a shell based on quartz glass and the protective coating, while the core is made of undoped quartz glass, the wavelength cutoff of the first high fashion specified fiber is not revised 1.7 mm, and the chlorine content in the core does not exceed 0.01 weight percent.

In addition, radiation-resistant optical fiber according to this aspect of the chlorine content in the core is larger than 1·10-5weight percent, and the amplitude of the absorption bands of hydroxyl OH-groups at the wavelength of 1.38 μm in the spectrum of the optical loss of the fiber does not exceed 9 dB/km Sheath of the inventive fiber may consist of outer and inner shell or only the inner shell. While the inner shell may be made of quartz glass doped with fluorine, and contain an annular region adjacent to the core, the refractive index of which is less than the core refractive index is not more than 0,006. It is advisable that while in the inner membrane had the ring region, the refractive index of which is less than the core refractive index more than 0,007. Radiation-resistant optical fiber can be microstructured or photonic crystal or birefringent.

According to a second independent aspect of the invention, a method of manufacturing radiation-resistant fiber of the optical fiber based on silica glass, comprising the manufacture of a workpiece containing a core and a shell, using the same process of chemical deposition of caravag the glass of a mixture of a source of gaseous reagents, and subsequent stretching of the preform of the fiber, and the synthesis of the glass core are from a mixture of silicon tetrachloride and molecular oxygen and provide excess molar flow rate of molecular oxygen on a molar flow rate of silicon tetrachloride at least 75 times.

Thus it is possible to carry out chemical precipitation of quartz glass on the inner surface of the support pipe of undoped or doped with fluorine quartz glass, which is the outer sheath of the fiber, which, in particular, remove the front hood of the light guide. It is advisable to synthesize membrane of a mixture of a source of gaseous reagents containing silicon tetrachloride, tetraploid silicon and molecular oxygen, and the region of the shell adjacent to the core, it is advisable to synthesize using direct deposition of silica glass doped with fluorine, and the peripheral region of the shell by means of impregnation of the porous layer of the quartz glass of silicon tetrafluoride.

According to a third independent aspect of the invention, a method for improving the radiation resistance of the fibre on the basis of quartz glass containing a core, a cladding and a protective coating, the core of the workpiece which is made by chemical vapor deposition of silica glass from a mixture of source is x gaseous reagents, containing silicon tetrachloride and molecular oxygen, and in the above-mentioned mixture to provide a molar excess consumption of molecular oxygen on a molar flow rate of silicon tetrachloride at least 75 times.

It is expedient in this case, the shell of the workpiece to also synthesize by chemical vapor deposition of silica glass from a mixture of a source of gaseous reagents containing, for example, silicon tetrachloride, tetraploid silicon and molecular oxygen. In this case, the area of the shell adjacent to the core, it is useful to synthesize using direct deposition of silica glass doped with fluorine, and the peripheral region by means of impregnation of the porous layer of the quartz glass of silicon tetrafluoride. It is also advisable to carry out the deposition of the core and the shell on the inner surface of the support pipe of undoped or doped with fluorine quartz glass.

According to the fourth independent aspect of the invention, a method for improving the radiation resistance of the fibre on the basis of quartz glass containing a core, a cladding and a protective coating, the core of the workpiece which is made by chemical vapor deposition of silica glass from a mixture of a source of gaseous reagents containing silicon tetrachloride, molecular oxygen and tetraploid Rennie, moreover, in the above-mentioned mixture to provide a molar excess consumption of molecular oxygen on a molar flow rate of silicon tetrachloride at least 70 times.

It is advisable when this shell blanks also to synthesize by chemical vapor deposition of silica glass from a mixture of a source of gaseous reagents containing, for example, silicon tetrachloride, tetraploid silicon and molecular oxygen. In this case, the area of the shell adjacent to the core, it is useful to synthesize using direct deposition of silica glass doped with fluorine, and the peripheral region by means of impregnation of the porous layer of the quartz glass of silicon tetrafluoride. It is also advisable to carry out the deposition of the core and the shell on the inner surface of the support pipe of undoped or doped with fluorine quartz glass. It is also possible to mix the original gaseous reagents in the synthesis of the core to add freon 113.

According to the fifth independent aspect of the invention, a method for improving the radiation resistance of the fibre on the basis of quartz glass containing a core, a cladding and a protective coating, the core of the workpiece which is made by chemical vapor deposition of silica glass from a mixture of a source of gaseous reagents containing silicon tetrachloride, molecularly oxygen and freon 113, moreover, in the above-mentioned mixture to provide a molar excess consumption of molecular oxygen on a molar flow rate of silicon tetrachloride at least 70 times.

It is advisable when this shell blanks to synthesize by chemical vapor deposition of silica glass from a mixture of a source of gaseous reagents containing, for example, silicon tetrachloride, tetraploid silicon and molecular oxygen. In this case, the area of the shell adjacent to the core, it is useful to synthesize using direct deposition of silica glass doped with fluorine, and the peripheral region by means of impregnation of the porous layer of the quartz glass of silicon tetrafluoride. It is also advisable to carry out the deposition of the core and the shell on the inner surface of the support pipe of undoped or doped with fluorine quartz glass. It is also possible to mix the original gaseous reagents in the synthesis of core add tetraploid silicon.

Thus, the inventive radiation-resistant optical fiber, method of manufacturing and method of improving the radiation resistance of optical fiber overcome the shortcomings identified unique.

Brief description of drawings

In Fig.1 shows a longitudinal section of the inventive fiber.

In Fig.2 schematically presents the profiles of the refractive index sotovogo is, described in the example implementation, including the inventive fiber.

In Fig.3 shows the spectrum of the initial (measured before exposure to gamma radiation) optical loss in the inventive radiation-resistant optical fiber.

In Fig.4 presents RNP at the wavelength of 1.31 μm, and Fig.5 - RNP at the wavelength of 1.55 μm, measured in the prototype fiber manufactured according to the present invention, and in five other fibres, manufactured and tested in order to compare, in the process of gamma irradiation optical fibers within 180 minutes and relaxation within 30 minutes after cessation of exposure.

The implementation of the invention

In Fig.1 the positions are indicated: 1 - core, 2 - inner sheath, synthesized from a mixture of a source of gaseous reagents, 3 - outer shell formed by the material of the support pipe, 4 - protective coating. Also shown is the diameter of the outer shell d. Thus, the shell comprises an inner shell 2 and outer shell 3. The outer shell 3 may be absent if the deposition of the inner shell 2 is not held on the inner surface of the support pipe, or if the outer shell 3 has been removed before pulling the fiber. In this case, the shell means only the inner shell 2.

The dashed line in Fig.1 and Fig.2A-C show the border of the two circular regions with different indicator p is elmline in the inner shell 2. The presence of such areas is possible embodiment of the invention, and the position of the 5 marked the annular area of the inner shell 2 adjacent to the core 1, and the position of the 6 - ring area of the inner shell 2 that do not belong to the core 1, i.e., which is peripheral.

An example of carrying out the invention

Technology MCVD, in which the core and the inner shell preform synthesized by precipitation of quartz glass from a mixture of a source of gaseous reactants on the inner wall of the support pipe made of quartz glass, produced six blanks, which were then stretched fiber optical fibers a, B, C, G, D and E. a prototype fiber E was manufactured according to the present method of manufacture and is an example of the inventive radiation-resistant fiber-optic waveguides. It is worth emphasizing that the core and the inner shell of each of the billets was synthesized under the same process.

The deposition of the synthesized glass in the MCVD process was carried out on a support tube made of undoped quartz glass F300 company Heraeus (samples a, B, C, D, E), or a support tube made of quartz glass doped with fluorine, F520-28 company Heraeus (samples C, D). The external diameter of the pipe was 25 mm, and the thickness of their walls 2 mm.

First on the supporting pipe-known method is repicci porous layer of quartz glass, silicon tetrafluoride (see A. N. Guryanov, M. Y. Salansky, C. F. Chopin, A. F. Kosolapov, S. D. Semenov. "Vysokoaperturnykh the optical fibers based on silica glass doped with fluorine". Inorganic materials, volume 45, No. 7, S. 887-891 (2009)) layers deposited inner sheath 2 made of quartz glass doped with fluorine, and then the core 1 of undoped silica glass (in the case of samples a, D, E) or silica glass doped with fluorine (samples B, C, D).

When the deposition of each individual layer of the inner shell 2 first by movement of the burner towards the flow of the mixture of the source of gaseous reactants at a speed of 120 mm/min was deposited porous layer of undoped quartz glass when serving in a support tube of silicon tetrachloride and molecular oxygen (the flow rate of the last 2500 ml/min was constant during the synthesis of the shell for all samples). After this was done the penetration deposited porous layer while moving the burner in the direction of flow of the mixture of the source of gaseous reactants at the same speed and when applying to a support tube of silicon Tetra-fluoride (for all samples) and addition of molecular oxygen (in the case of samples a and B). As a result of this procedure was achieved by doping quartz glass with fluorine so that the refractive index of the synthesized fertilitate inner shell after the collapse of the preform was about 0,009 less than the refractive index of undoped quartz glass core. Areas 5 and 6 with different refractive index in the inner shell 2 did not.

After the deposition of the glass layers of the inner shell 2 has precipitated two layer glass core 1. In the reference pipe were submitted silicon tetrachloride and molecular oxygen; for sample B was further submitted freon 113 at a flow rate of 2 ml/min and samples C and D - tetraploid silicon at the rate of 155 and 445 ml/min, respectively. The burner is moved contravene with the flow of the reactants at a speed of 120 mm/min, the Deposition of quartz glass when co-directed the flow of reagents and the burner is called "direct deposition". As a result of the process in samples B, C and D was synthesized core 1 made of quartz glass doped with fluorine in different concentrations, and the samples A, D and E was synthesized core 1 of undoped silica glass (see table).

The table shows the technological modes of harvesting the fiber produced according to this invention, and five other blanks of optical fibers, made for the purpose of comparison, the concentration of chlorine and fluorine in the core of the workpieces measured by electron microscope with x-ray analyzer, chemical composition, and the diameters of the respective optical fibers. Technological modes shown in the table, along with the data in the description of p is of iMER, allow to reproduce the claimed objects of the invention.

In the columns of the table shows the following (left to right): denote blanks/optical fibers a, B, C, D, E, f, the number of layers q quartz glass doped with fluorine, in the shell 2, the flow rate of silicon tetrachloride η(SiCl4) in the deposition of the porous layer of the membrane 2, the flow rate of silicon tetrafluoride η(SiF4) when the penetration of the porous layer of the membrane 2, the consumption of molecular oxygen η(O2) when the penetration of the porous layer of the membrane 2, the temperature T1penetration of the porous layer of the membrane 2, the flow rate of silicon tetrachloride ξ(SiCl4) during the synthesis of the layers of the core 1, the consumption of molecular oxygen ξ(O2) during the synthesis of the layers of the core 1, the flow rate of silicon tetrafluoride ξ(SiF4) during the synthesis of the layers of the core 1, the ratio r of molar expense of molecular oxygen and silicon tetrachloride in the synthesis of core layers 1, temperature T2deposition of the layers of the core 1, the fluoride concentration C(F) and chlorine (C(Cl) in the core 1, measured in the blanks, and the diameter d of the optical fibers.

When the deposition of the core 1 from the workpiece to the workpiece changed the ratio g molar flow rate of molecular oxygen to the molar flow rate of silicon tetrachloride (see table). A commonly used ratio of 37...56 used in the case of sample a, The sample On the flow of oxygen b is l intentionally low (r=20). This has led to the highest chlorine content in the core 1 of all samples (C(Cl)=0,0230 wt.%). Samples B and E. the consumption of oxygen was highest (r=70 and 75, respectively). In the case of the inventive fiber E this has led to a marked reduction in the concentration of chlorine in the core 1 (C(Cl)=0,0086 wt.%), which turned out to be the smallest of all samples. Therefore, the inventive method of manufacturing the optical fiber really helps to suppress the occurrence of chlorine in the glass. In sample B reduce the concentration of chlorine did not happen, because the chlorine addition was present in freon 113, which was added to the mixture of the source of gaseous reagents. It should be noted that the addition of silicon tetrafluoride in the mixture, as expected, also led to the suppression of occurrence of chlorine in the glass core 1 (sample G, C(Cl)=0.0087 wt.%).

Upon completion of the deposition process of the glass core 1 tubular glass blank was subjected to compression in one or two passes of the burner at a rate of ~15...30 mm/min, when the temperature of the outer surface of the workpiece over 2,200°C to visually minimum diameter of the inner capillary. After this, at a temperature of ~2200°C and speed of the burner several mm/min, under the forces of surface tension and the temperature lowering of the viscosity of the glass was the collapse of the tubular workpiece in a continuous erased the Yan, what was the end of the manufacturing process of the workpiece.

From billets pulled the fibers with the application in the process of drawing a protective polymer coating 4. The exhaust velocity was 40 m/min, the tension draft - 65,

The fibers were single in the near infrared range with a wavelength cutoff of the first high fashion is no longer of 1.65 μm. Range of optical loss in the inventive optical fiber shown in Fig.3. Optical losses on the most relevant wavelengths of 1.31 and 1.55 μm amounted to 0.35 and 0.34 dB/km, which corresponds to the international standard.

17
Table
Designation preform/ fiberThe parameters of the deposition of the shell 2The deposition parameters and properties of the core 1
qη(SiCl4), ml/minH(SiF4), ml/minη(O2), ml/minT1, °Cξ(SiCl4) ml/minξ(O2) ml/minξ(SiF4) ml/minrT2, °CC(F), wt.% C(Cl) wt.%d, µm
And234001001702090452500-56220000,0192140
B23400501122070503500-7023000,200,0216145
In1750050-71406725001553721000,410,0123150
G51750-21106725004453721500,650,0087150
D2340050-2070501000-20217000,0230133
E2040050-2100675000-75220000,0086125

The profile of the refractive index of the blanks and the corresponding optical fibers is schematically shown by the solid line in Fig.2A (for the image of the s And, D and E) of Fig.2B (for sample B), and Fig.2B (for samples C and D). The refractive index of the core 1 of the inventive radiation-resistant svetovoda E was is 0.0002 below the refractive index of the outer shell 3 formed in this particular example, the material of the support pipe F300. However, in General the implementation of the inventive radiation-resistant optical fiber, the refractive index of the core 1 may be both more and less than the refractive index of the outer shell 3 or equal to that determined primarily by the properties of the quartz glass support tube and the presence of alloying elements such as fluorine.

The authors also found that for matching spot size fashion inventive waveguide with dimensions of standard spots of fibers and further improve the radiation resistance of the inventive fiber is advisable to produce the inner shell 2 of the two annular regions 5 and 6 with different refractive index. It is reasonable that the refractive index of the annular area 5 of the inner shell 2 adjacent to the core 1, was lower than the refractive index of the core 1 is not more than 0,006. This annular region 5 should synthesize the direct deposition of silica glass doped with fluorine, adding to the mixture of the source gas SiCl 4O2and SiF4. In the peripheral annular region 6 of the inner shell 2, the refractive index must be lower than the refractive index of the core 1, at least 0.007 s in order to avoid bending losses in optical fiber with a strong bending of the fiber. This annular area 6 should be synthesized by impregnation of a porous layer of silica glass with silicon tetrafluoride.

The optical fibers a, B, C, G, D, E were irradiated from a source of gamma radiation from cobalt-60 for 180 minutes at a dose of 0.75 Gy/s and at room temperature to a dose of 8.1 rag and during irradiation was measured value of the RPP. After 180 minutes of irradiation was stopped, and for a further 30 minutes was measured RNP in the absence of radiation.

As can be seen in Fig.4, the suppression of occurrence of chlorine in the glass in the invention leads to the suppression RNP-1: unlike fiber D with a high content of chlorine and therefore pronounced RNP-1 (monotonic increase RNP with increasing dose), and the proposed fiber E RNP-1 was not observed.

The proposed methods allow to suppress and RNP-2. This is demonstrated by the comparison of Fig.4 and 5 are curves for RNP fiber G with a core 1 made of quartz glass doped with fluorine, and curves RNP for the proposed fiber F with unalloyed core 1 made of quartz glass. These fibers contain almost the same small amounts, the creation of chlorine, however, RPP significantly more fiber G than the proposed fiber E (Fig.3). When this form RNP in sample G, we can conclude that it is due RNP-2, the distinguishing feature of which is the non-monotonic dependence on the dose. Meanwhile, the proposed fiber E signs nonmonotonic turn RNP depending on the dose practically does not occur, therefore PPR-2 of the inventive fiber is suppressed almost completely.

The inventive fiber is suppressed and RNP-3. To be sure, made the following observation: within 15 minutes after completing the above irradiation compared RNP in optical fibers a, B, C, G, D, E on the wavelength of 1.7 μm, in which the determining mechanism is RNP-3. It turned out that the inventive light conductor E. as well as that of the optical fibers B, C, D with a core 1 made of quartz glass doped with fluorine, RNP was about 3 dB/km, the light guide A - 6 dB/km, the light guide D - 10 dB/km Therefore, the inventive method allows to suppress RPN-3 no worse than the method which consists in alloying of the core 1 by fluorine.

Thus, the inventive fiber suppressed all three mechanisms RNP (RNP-1, 2 and 3). As follows from Fig.4 and 5, the two most used for optical communication wavelengths of 1.31 and 1.55 μm, the inventive fiber E shows the lowest RNP of the six optical fibers a, B, the, G, D, E, ie, the highest radiation resistance.

In the example implementation of a close analogue for U.S. patent 7689093 B2 described radiation-resistant optical fiber, demonstrated RNP ~9 dB/km at the dose of ~8,1 kGy and dose rate is 0.22 G/s (wavelength of 1.31 μm). The inventive fiber E showed when the same dose is almost the same RNP (10 dB/km, Fig.4), but, importantly, at dose rate of 3.4 times greater (0.75 Gy/s). It is known that optical fibers with non-alloy core and a core doped with fluorine, RNP strongly decreases with decreasing dose rate. Therefore, when the dose rate is 0.22 G/s in the inventive fiber RNP would be significantly less than the dose of 0.75 Gy/s and, therefore, less than the specified analog. Thus, the inventive fiber is superior in radiation resistance of the fiber-equivalent.

You should pay attention to the RPP in the fiber B, obtained at considerable excess of oxygen in a mixture of initial reagents (r=70), which in this case contained more and freon 113. In the core was doped with fluorine. However, it is easy to see that a relatively high radiation resistance of the optical fiber B is not due to admixture of fluorine in the core (fiber optic cables and D contain more fluoride, but showed a lower radiation resistance, see Fig.4, 5 and table), and a significant excess color is Yes in the synthesis of the core. Therefore, in addition to the method of manufacturing a radiation-resistant optical fiber with a core of undoped quartz glass also claimed variants of the method of improving the radiation resistance of the fibre, manufactured with a core of undoped or doped with fluorine quartz glass.

The inventive radiation-resistant neporojny the optical fiber, method of manufacturing and method of improving the radiation resistance of the fibre can be implemented using other known technological processes of chemical vapor deposition of silica glass from a mixture of a source of gaseous reagents, such as FCVD, VAD, OVD, PCVD, SPCVD. It should be noted that the FCVD process consisting in the chemical deposition of quartz glass on the inner surface of the support pipe is essentially just a variant of realization of the MCVD process, differing only by way of heating of the support pipe (see A. A. Malinin, A. S. Zlenko, L. G. Akhmetshin, S. L. Semjonov "Furnace chemical vapor deposition (FCVD) method for special optical fibers fabrication", Proc. SPIE, vol.7934, paper 793418 (2011)).

Radiation resistance of the inventive fiber-optic waveguides satisfies modern requirements for radiation-resistant fiber light guides with their practical applications. For example, the inventive radiation-resistant fiber light guide m which can be applied in the Large hadron Collider, where the fiber is exposed nuclear and ionizing radiation. It is known that for this application you need the fiber light guide with an optical loss at the dose of 100 kGy not more than 7 dB/km at low dose (less 0,0003 G/s) at the operating wavelength of 1.31 μm (see T. Wijnands, L. K. De Longe, J. Kuhnhenn, S. K. Hoeffgen, U. Weinand "Optical absorption in commercial single mode fibers in a high energy physics radiation field", IEEE Transactions on Nuclear Science, vol.55, pp.2216-2222 (2008)). The authors have conducted an additional experiment in which the inventive fiber E was irradiated to a dose of more - 1.31 Mg (dose rate was 0.73 G/s). Optical loss in the inventive radiation-resistant optical fiber F through 6 days after such exposure was only 10 dB/km considering the fact that irradiation was conducted to dose by more than an order of magnitude higher than the dose used in the Large hadron Collider, and with much greater dose rate, we can conclude that the above operating conditions of the inventive radiation-resistant fiber light guide would be many times smaller RNP. Thus, it satisfies the requirements for fiber light guide, intended for practical use in the Large hadron Collider.

1. Radiation-resistant fiber fiber containing a core and a shell based on quartz glass and protective p is a covering, when this core is made of undoped quartz glass, the wavelength cutoff of the first high fashion specified fiber not over 1.7 μm, and the chlorine content in the core does not exceed 0.01 weight percent.

2. The fiber under item 1, in which the chlorine content in the core is larger than 1·10-5weight percent.

3. The fiber under item 1, in which the amplitude of the absorption bands of OH groups at the wavelength of 1.38 μm in the spectrum of the optical loss of the fiber does not exceed 9 dB/km

4. The fiber under item 1, in which the shell consists of an outer and inner shell or the inner shell.

5. The fiber under item 4, in which the inner shell is made of quartz glass doped with fluorine.

6. The fiber under item 5, in which the inner shell includes an annular region adjacent to the core, the refractive index of which is less than the core refractive index is not more than 0,006.

7. The fiber under item 6, in which the shell contains an annular region, the refractive index of which is less than the core refractive index more than 0,007.

8. The fiber under item 1, which is microstructured.

9. The fiber under item 1, which is the photonic crystal.

10. The fiber under item 1, which is birefringent.

11. A method of manufacturing a radiation-resistant fiber of the optical fiber based on marcavage glass, includes the manufacture of the workpiece containing the core and the shell, using the same process of chemical deposition of quartz glass from a mixture of a source of gaseous reactants and subsequent stretching of the preform of the optical fiber, and the synthesis of the glass core are from a mixture of silicon tetrachloride and molecular oxygen and provide excess molar flow rate of molecular oxygen on a molar flow rate of silicon tetrachloride at least 75 times.

12. The method according to p. 11, in which the chemical precipitation of quartz glass are on the inner surface of the support pipe of undoped or doped with fluorine quartz glass, which is the outer shell of the light guide.

13. The method according to p. 12, in which the outer shell blanks are removed before extraction of the light guide.

14. The method according to p. 11, in which the shell is synthesized from a mixture of a source of gaseous reagents containing silicon tetrachloride, tetraploid silicon and molecular oxygen.

15. The method according to p. 14, in which the area of the shell adjacent to the core, synthesized by direct deposition of silica glass doped with fluorine, and the peripheral region of the membrane are synthesized by impregnation of a porous layer of silica glass with silicon tetrafluoride.

16. A method of improving the radiation resistance of the fibre is and the basis of quartz glass, containing a core, a cladding and a protective coating, the core of the preform which is produced by ohmic deposition of quartz glass from a mixture of a source of gaseous reagents containing silicon tetrachloride and molecular oxygen, and in the above-mentioned mixture to provide a molar excess consumption of molecular oxygen on a molar flow rate of silicon tetrachloride at least 75 times.

17. The method according to p. 16, in which the envelope blanks are synthesized by chemical vapor deposition of silica glass from a mixture of a source of gaseous reactants.

18. The method according to p. 17, in which the synthesis of lead from a mixture of gaseous reactants containing silicon tetrachloride, tetraploid silicon and molecular oxygen.

19. The method according to p. 18, in which the area of the shell adjacent to the core, synthesized by direct deposition of silica glass doped with fluorine, and the peripheral region of the membrane are synthesized by impregnation of a porous layer of silica glass with silicon tetrafluoride.

20. The method according to p. 17, in which the chemical precipitation of quartz glass in the synthesis of the core and the shell are on the inner surface of the support pipe of undoped or doped with fluorine quartz glass.

21. A method of improving the radiation resistance of the fibre on the basis of quartz glass, terasawa core, the shell and the protective coating, the core of the workpiece which is made by chemical vapor deposition of silica glass from a mixture of a source of gaseous reagents containing silicon tetrachloride, molecular oxygen and tetraploid silicon, and in the above-mentioned mixture to provide a molar excess consumption of molecular oxygen on a molar flow rate of silicon tetrachloride at least 70 times.

22. The method according to p. 21, in which the envelope blanks are synthesized by chemical vapor deposition of silica glass from a mixture of a source of gaseous reactants.

23. The method according to p. 22, in which the synthesis of lead from a mixture of gaseous reactants containing silicon tetrachloride, tetraploid silicon and molecular oxygen.

24. The method according to p. 23, in which the area of the shell adjacent to the core, synthesized by direct deposition of silica glass doped with fluorine, and the peripheral region of the membrane are synthesized by impregnation of a porous layer of silica glass with silicon tetrafluoride.

25. The method according to p. 22, in which the chemical precipitation of quartz glass in the synthesis of the core and the shell are on the inner surface of the support pipe of undoped or doped with fluorine quartz glass.

26. The method according to p. 21, in which a mixture of a source of gaseous reagents add freon 113.

27. Methods for the improvement of radiation resistance of the fibre on the basis of quartz glass, containing a core, a cladding and a protective coating, the core of the workpiece which is made by chemical vapor deposition of silica glass from a mixture of a source of gaseous reagents containing silicon tetrachloride, molecular oxygen and freon 113, and moreover, in the above-mentioned mixture to provide a molar excess consumption of molecular oxygen on a molar flow rate of silicon tetrachloride at least 70 times.

28. The method according to p. 27, in which the envelope blanks are synthesized by chemical vapor deposition of silica glass from a mixture of a source of gaseous reactants.

29. The method according to p. 28, in which the synthesis of lead from a mixture of gaseous reactants containing silicon tetrachloride, tetraploid silicon and molecular oxygen.

30. The method according to p. 29, in which the area of the shell adjacent to the core, synthesized by direct deposition of silica glass doped with fluorine, and the peripheral region of the membrane are synthesized by impregnation of a porous layer of silica glass with silicon tetrafluoride.

31. The method according to p. 28, in which the chemical precipitation of quartz glass in the synthesis of the core and the shell are on the inner surface of the support pipe of undoped or doped with fluorine quartz glass.

32. The method according to p. 27, in which a mixture of a source of gaseous reagents add tetraf arid silicon.



 

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