RU2363668C2 - Method for making of fiber light guides workpieces, device for its implementation and workpiece fabricated thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention refers to the method for workpieces making of W-type single- and multimode fiber light guides. The method is implemented by the plasmochemical precipitation of the deeply depressed fluorosilicate shell SiO₂-F with (Δn=-2.5%) and quartz core to the inner surface of optically pure support tube which surface beforehand undergoes chemical, flame and microwave plasma treatment (using "cold", non-equilibrium, evenly ionised reduced pressure microwave plasma). The gas mixtures O₂ and SiCl₄+C₃F₈ (reflecting shell), then SiCl₄+O₂ (core) are supplied successively into the tube. The method is implemented with the help of device having the device for microwave radiation input with rotation of polarisation plane or polariser mounted in front of plasmotron entrance. The source of microwave energy is wide-band transistor amplifier with electrically tunable driving oscillator and electrically controlled afile:///C:\\Temp\\Word_2 mounted between amplifier and oscillator.

EFFECT: efficiency enhancing of the fabrication process of light guides having the necessary refractive index profile.

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Description

The invention relates to a method for producing blanks of optical fibers and can be used to create highly informative communication systems, fiber lasers, amplifiers and fiber-optic sensors for monitoring various physical quantities (temperature, electromagnetic and magnetic fields, mechanical stresses and displacements, and other parameters).

Known methods and devices for the manufacture of quartz blanks in a plasma of a microwave discharge of low pressure (PCVD methods) of optical fibers, including those with a deeply depressed fluorosilicate cladding, characterized by a significantly lower refractive index (PP) compared to a silica glass PP equal to Δn - 2% [1. P. Geittner et.al. "Appl. Phys. Lett.", V. 28, 11, 1976. 2. German Patent No. 2444100, C03B 37/018, 03/25/1976. 3. DE No. 3632684 H056 / 80, 03/31/1988. 4. EP No. 0086533 C03B 37/018, 08.24.1983].

The high PCVD method inherent in the high deposition efficiency of pure SiO ₂ and fluorine-doped SiO _{2 is} also well known. An important advantage of SiO ₂ / SiO ₂ -F optical fibers obtained by this method is the absence of a dip in the refractive index profile (PPP), low optical loss, high numerical aperture (NA = 0.3), and weak bending sensitivity in single-mode optical fibers (OVS).

However, the excellent and unchanged dispersion properties of W-type OWS can be obtained only with a significant increase in the depth of the depressed shell using the most effective fluorine-containing reagents and the optimum surface temperature of the supporting quartz tube.

W-type fibers with a deeply depressed cladding, especially for OVSs, can be fabricated using the PCVD method with either a pure quartz core or alloying a quartz core with germanium and fluorine.

Using well-known thermal methods for manufacturing fiber-optic fiber blanks (MCVD, OVD, VAD, atmospheric-pressure PCVD), it was not possible to optimize the refractive index profile (PPP) for various parameters for both multimode optical fibers (MVS) and single-mode optical fibers (OVS) ) to achieve high optical properties of light guides, in particular dispersion, the composition of SiO ₂ / SiO ₂ -F, SiO ₂ + GeO ₂ / SiO ₂ -F, due primarily to the inability to obtain these methods deeply depressirovannoy fluorosilicate reflective hull and.

The method claimed in patent EP 0086533 C03B 37/018, 08.24.1983, is the closest analogue of this invention. The essence of this method is as follows: a low-pressure microwave plasma (1-25 torr) created by a microwave plasmatron at a frequency of 2450 MHz creates a local reaction zone inside the supporting quartz tube, which, when it moves back and forth, deposits thousands of compact concentric layers of quartz glass inside the tube . The starting materials are: SiCl ₄ , GeCl ₄ , C ₂ F ₆ and O ₂ . The temperature of the support pipe during deposition varies from 1100 ° C to 1200 ° C. After the deposition is completed, the tubular billet collapses into the stand using a gas burner at a temperature of 2000-2200 ° C. In the manufacture of OVS, the external diameter of the workpiece is increased by the procedure of clapping outside an additional quartz tube.

The main doping fluorine-containing reagent, with the help of which all the main results on the SPT optimization were obtained, was C ₂ F ₆ freon, and the main device used to deposit various optical structures was first the simplest waveguide device on an H ₁₀ wave with a short-circuit piston at the end and thermal sections of the furnace above and below the waveguide, and hereinafter - the device on the wave H ₀₁ (type of resonator vibrations

H ₀₁₁ ) located and moved in a thermal furnace.

However, despite the high achievements in creating W-type optical fibers with a deeply depressed cladding, doping of the reflecting quartz cladding with fluorine using C ₂ F ₆ freon made it impossible to achieve its maximum fluorine doping, i.e. to achieve the greatest depth of the depressed shell (Δn did not exceed -2%).

The use of a waveguide device based on the H ₁₀ wave as a microwave plasma torch was not effective in many respects (low deposition rate, limited diameter of the quartz support tube and, first of all, inefficient use of an optically clean and expensive support quartz tube (not more than 40-50%)) . A device of type H _{011 is} suitable for deposition inside pipes of only a large diameter (40-43 mm), since the electric field along the axis of the resonator is E = 0 and reaches its maximum value at a distance of ~ R / 2, where R is the radius of the resonator.

In this case, the supporting quartz tubes must have an internal diameter of at least 40 mm (tube diameter 45 × 40 mm). This presents certain difficulties in the implementation of the PCVD method for the following reasons:

1. Industry does not produce optically pure pipes with a diameter of 45x40 mm or more.

2. The power of the generator at a frequency of 2450 MHz for the creation of microwave plasma and the deposition of optical structures in a supporting quartz tube with a diameter of 45 × 40 mm or more should be 10-15 kW. Accordingly, the weight of the generator unit and its size increase, which presents technical difficulties in the high-quality implementation of the PCVD process.

3. There is a technical problem of collapse of such tubular blanks.

4. The optimization of the optical parameters of W-type optical fibers with a deeply depressed cladding is complicated in this case.

A prototype of the present invention is a method for manufacturing fiber blanks in which a fluorosilicate reflective sheath is applied using a “cold” nonequilibrium microwave plasma to the surface of a cylindrical quartz glass rod (US 6988380, C03B 37/014, 2004-02-19).

This method does not allow to obtain blanks with acceptable performance for single-mode W-type fiber waveguides with the necessary profile of the refractive index, with increased broadband.

The objective of this invention is to provide a method for the manufacture of quartz blanks of fiber optical fibers, both multimode (MVS) and single-mode (OVS) with a pure quartz core, with a core doped with germanium and fluorine, as well as a quartz core doped with various rare-earth metals (neodymium, erbium, terbium ), one, two or more elements and additives to them, such as potassium, aluminum, phosphorus, germanium, nitrogen, fluorine, both individually and in various combinations, with a more deeply depressed fluorosilicate reflecting shell Coy, than the prototype method.

To solve the problem and achieve greater depth of the fluorosilicate depressed cladding, a method is proposed for manufacturing prefabricated W-type single-mode and multimode fiber optical fibers by plasma-chemical deposition of a deeply depressed fluorosilicate cladding SiO ₂ -F and a silica core SiO ₂ with Δn equal to -2.5%, using “Cold” nonequilibrium, uniformly ionized plasma of a microwave discharge of reduced pressure on the inner surface of an optically clean supporting quartz tube, which was previously subjected chemical, fire and microwave plasma-chemical treatment, and then sequentially inside the pipe into the microwave discharge at a temperature of 1050 ° C serves a mixture of gases O ₂ and SiCl ₄ + C ₃ F ₈ for the formation of a reflective shell and at a temperature of 1200 ° C a mixture of SiCl ₄ gases + O ₂ for the formation of the quartz core of the workpiece during the reciprocating movement of the microwave plasma with the resonator TE ₁₁₁ (H ₁₁₁ ) along the pipe with a speed of 2.0-3.5 m / min and rotation of the supporting quartz pipe with a speed of 0.5-1 r / min

In the proposed method, the quartz core can be alloyed with germanium and fluorine, as well as various rare earth metals from the group containing neodymium, erbium, ytterbium, and additives to them selected from the group containing potassium, aluminum, phosphorus, germanium, nitrogen, fluorine, as individually and collectively in various combinations, volatile compounds of rare-earth metals, mainly organometallic compounds with high vapor pressure, are used as starting reagents.

The level of fluorine penetration during the formation of a reflecting shell in a plasma of a microwave discharge of reduced pressure is determined by the deposition rate, the surface temperature of the supporting quartz tube, microwave power, the type of freon and its concentration level, pressure, and flow rate of the reagents.

In the present invention, C ₃ F ₈ freon is used as the fluorine-containing reagent, which makes it possible to obtain a workpiece of the composition SiO ₂ / SiO ₂ -F with Δn equal to -2.5% (NA = 0.33) under the proposed modes of the method for manufacturing the workpiece.

Precipitation of pure quartz glass to form the core of the preform, in contrast to the deposition of fluorosilicate glass during the formation of a fluorosilicate shell, is carried out at a surface temperature of the supporting quartz tube of 1200 ° C and a flow rate of O ₂ for bubbling SiCl ₄ 12 l / h. This allows you to get high quality quartz glass. The production time of the SiO ₂ / SiO ₂ -F preform is 3 hours (2 hours - SiO ₂ -F shells and 1 hour - cores).

The method proposed in the present invention is as follows.

Example 1

To prepare for the development of a supporting quartz tube with a diameter of 20 × 17 mm, it is preliminarily subjected to chemical and fire (heat) treatment, for which a mixture of O ₂ gases at a speed of 40 l / h and SF ₆ at a speed of 15 l / h is fed into the pipe. Using a hydrogen-oxygen burner, the supporting quartz tube is heated to a softening temperature, after which its surface (after 3 passes of the burner) becomes clean both inside and outside. Next, the burner is removed, the furnace is lowered and heating is turned on, the pipe is sealed and vacuum to a pressure of 1-3 Torr. Before deposition of the SiO ₂ -F shell at a furnace temperature of 1000 ° C, microwave plasma is ignited and a mixture of O ₂ at a speed of 60 l / h and CCl ₄ at a speed of 3 l / h are fed into the discharge at a pressure of 3-5 Torr. Thus, a soft plasma etching of the inner surface of the support pipe is carried out, in which organic and inorganic compounds, dirt and dust are removed and, most importantly, the substrate is activated (the surface inside the support pipe). Finish the treatment of the inner surface of the pipe by polishing in the microwave plasma of oxygen. After that, the temperature of the supporting quartz tube is raised to 1050 ° C and the process of deposition of the reflecting fluorosilicate shell on its inner surface is started at a pressure of 6-8 Torr. For the deposition of the fluorosilicate shell, the support quartz tube is rotated at a speed of 0.5-1 rpm, along it with a power of a microwave source of 800 W at a speed of 2.5-3.0 m / min, the TE ₁₁₁ resonator is reciprocated ₁₁₁ ). At a temperature of 1050 ° C, a mixture of O ₂ and SiCl ₄ + C ₃ F ₈ gases is fed into the microwave discharge into the support quartz tube to form a fluorosilicate reflective shell on its inner surface. Then the temperature is raised to 1200 ° C. and a mixture of SiCl ₄ + O ₂ gases is fed into the supporting quartz tube with the fluorosilicate shell formed on its inner surface to form the quartz core of the workpiece. Next, the obtained tubular billet collapses, after which Δn of the billet is measured.

Example 2

The method is carried out in the same modes as in example 1. After deposition of the reflecting fluorosilicate shell, the formation of a quartz core is carried out from a vapor-gas mixture in the presence of SiCl ₄ + GeCl ₄ with a small addition of -C ₃ F ₈ .

The deposition of the silica core of SiO ₂ together with GeO ₂ and fluorine makes it possible to obtain a wide variety of MBF and WFM of the W type by varying Δ ⁺ and Δ ^- values. In addition, the fluorine supplement the core reduces the Rayleigh scattering and OH ^- absorption. Moreover, the efficiency of doping SiO _{2 with} germanium is 85%, fluorine 90-95%, and doping of the optical fibers with fluorine does not affect their optical properties. The use _of these two additives for doping SiO ₂ makes it possible to create a wide range of OVP SPP configurations with profile optimization in various parameters, which allows shifting the zero dispersion (λ ₀ ) to the region of lower optical loss - 1.55 μm and achieving low values of the total dispersion ( <2 psec / nm km).

Example 3

The proposed method involves alloying a quartz core with rare-earth metals to create active fibers. Volatile compounds of rare-earth metals with high vapor pressure, such as REM chlorides or preferably their volatile organometallic compounds of the formula ML ₃ nQ, where M is a rare-earth element, L is acetylacetonate ion, pivalate ion, iso -butylate ion; n is 1.3; Q - o-phenanthroline, α, α ′ - dipyridyl, pivalic, isobutyric acid. To improve the luminescent properties, various additives, such as potassium, aluminum, nitrogen, germanium, phosphorus, and fluorine, are introduced into pairs of volatile organometallic compounds.

In this example, the method is carried out in the same modes as in example 1, but at the end of the deposition of the fluorosilicate reflective shell, the formation of the quartz core is carried out in the presence of erbium erA ₃ Phen, diphenoylmethanate, neodymium NdA ₃ Phen or ytterbium YbA ₃ Phen with the addition of nitrogen, potassium or Germany, both individually and in various combinations. Pairs of compounds of rare earth metals and additives to them are served at a speed of 30 l / h.

Example 4

The method is carried out in the same modes as in example 1. After deposition of the fluorosilicate reflective shell, the formation of a quartz core is carried out in the presence of neodymium chloride of the formula NdCl ₂ 6H ₂ O or erbium chloride of the formula ErCl ₃ 6H ₂ O with the addition of aluminum, phosphorus or germanium as in individually, and in various combinations. Pairs of compounds of rare earth metals and additives to them are served at a speed of 30 l / h.

The deposition in a microwave plasma of a reduced pressure of a quartz core in the presence of rare-earth metal chlorides or organometallic compounds of rare-earth metals by one, two or more, both individually and in various combinations, allows achieving in active fibers:

- uniform deposition of alloying elements and additives,

- get sharp alloying profiles,

- achieve a high concentration and uniformity of the activator,

- to obtain a high numerical aperture of the glass fiber (0.45-0.5) due to partial doping of the core with nitrogen and rare-earth metals, and the shell - fluorine,

- achieve high deposition rates.

The table shows the optical characteristics of a quartz core doped with various organometallic compounds.

Figure 1 shows the dependence of Δn of the workpiece on the concentration of fluorine introduced and the temperature regime of the supporting quartz tube.

These parameters of the main stages of the method proposed in the present invention are given below.

The deposition of a deeply depressed fluorosilicate shell on the inner surface of the supporting quartz tube is carried out with the following parameters:

Pipe diameter mm 20 × 17 Pipe surface temperature, ° С 1050 Power of the microwave generator, W 800 The frequency of the microwave generator, MHz 2450 Pressure in a support pipe, torr 6-8 Oxygen consumption, l / hour 63,2 Oxygen consumption for bubbling SiСl ₄ , l / h 22.4 Consumption of Freon C ₃ F ₈ , l / h 1,5 Microwave plasma moving speed, m / min 2.0-3.0 The deposition length of the SiO ₂ -F shell, mm 600 Pipe rotation speed, rpm 0.5

The deposition of a pure quartz core on the inner surface of the supporting quartz tube with a previously deposited deeply depressed fluorosilicate shell SiO ₂ -F is carried out at the following parameters:

Furnace temperature, ° С 1200 Power of the microwave generator, W 800 Pressure in a support pipe, torr 6-8 Oxygen consumption, l / hour 63,2 Oxygen consumption for bubbling SiСl ₄ , l / h 12.0 Microwave plasma moving speed, m / min 2.0-3.0 Support pipe rotation speed, rpm 1,0

The obtained result of the use of the method of high-quality manufacturing of billets proposed in the present invention is illustrated in Fig. 1, which shows a curve of the dependence Δn of the billet on the concentration of fluorine introduced and the temperature regime of the supporting quartz tube.

The technical result of the invention is the large depth of the depressed fluorosilicate cladding (Δn = -2.5%), which allows to obtain higher and unchanged dispersion properties of the fibers, low optical loss, high numerical aperture NA = 0.33, low sensitivity to bending of the fibers without increasing Rayleigh scattering at λ _o = 1.3 μm.

Closest to the device proposed for the implementation of the method of manufacturing blanks of optical fibers by the PCVD method, the prototype is the device described in the copyright certificate No. 1573753, H05B 7/18, 06/15/1988

A device for producing blanks of fiber optical fibers consists of a resistance furnace, a resonator-type microwave plasmatron, holders of a supporting quartz tube connected to a system for preparing and supplying gas-vapor mixtures and a pumping system. The microwave plasmatron is made in the form of a resonator operating on the type of oscillation TE ₁₁₁ (H ₁₁₁ ), moved relative to the axis of the stationary support quartz tube and equipped with a mechanism for changing the length of the plasma zone, which is made in the form of two metal cylinders that shield the support quartz tube from exposure to microwave energy established with a gap between them and the possibility of regulating the gap. The choice of the TE ₁₁ (H ₁₁ ) wave is justified by the following features:

1. TE ₁₁ wave (H ₁₁ ) is the lowest type of wave in a circular waveguide and the second after TEM in coaxial. The absence of any field components that coincide in direction and phase for these two types of waves makes it possible to operate in a single-mode TE ₁₁₁ resonator (H ₁₁₁ microwave plasmatron) under waveguide excitation.

2. The TE ₁₁ (H ₁₁ ) wave has the maximum value of the Poynting vector P on the axis of the waveguide, which stimulates the discharge on the axis for any disturbing effects in the microwave plasmatron cavity filled with an absorbing plasma P _z ≠ 0, and has a maximum on the axis.

3. The TE ₁₁ (H ₁₁ ) wave in a coaxial structure, which is a cylindrical resonator with a conducting plasma on the axis, practically does not transform into a TEM wave, which reduces the microwave energy output through the side openings of the plasma torch and along the dielectric quartz elements (tube, rod).

4. The TE ₁₁ (H ₁₁ ) wave provides the maximum energy input into the plasma of the microwave discharge (ie, the ability to obtain the maximum value of E with the minimum contribution of the microwave power).

5. The microwave plasmatron on the TE ₁₁ (H ₁₁ ) wave has small dimensions. This device, however, has the following significant disadvantages:

1. The TE ₁₁ (H ₁₁ ) wave in this device does not have circular wave polarization, therefore, with azimuthal asymmetry of the TE ₁₁ (H ₁₁ ) wave, prerequisites are created for inhomogeneous deposition of the optical structures of the optical fibers, which negatively affects the performance of complex IFR optical fibers in the manufacture of single-mode and multimode blanks of W-type fibers with a deeply depressed fluorosilicate cladding and alloying with rare-earth metals and additives to them.

2. A magnetron generator at a frequency of 2450 MHz is used as a source of microwave radiation, which has a sufficiently large weight and dimensions; therefore, the process of moving a magnetron generator with a resonator is quite energy-intensive, but the most important thing is that the deposition at the pipe ends is not uniform when switching the resonator path.

3. Since the magnetron generator does not have the ability to tune in frequency, in order to maintain the resonant nature of the operation of the microwave plasma torch on the type of oscillations TE ₁₁₁ (H ₁₁₁ ), it is necessary to mechanically adjust the resonator during a long deposition process. The process of this tuning method is inertial and can not always be realized, since a lot of factors affect the resonant nature of the microwave plasma torch (change in the concentration of chemicals, pressure of the working gas and its flow velocity through the support tube, change in the speed of the reciprocating movement of the resonator and the temperature thermal furnace mode).

To obtain blanks of optical fibers according to the method proposed in the present invention, there is provided a device comprising a furnace, a quartz support tube located therein, a vapor-gas mixture supply system, a vacuum system, a microwave generator and a microwave plasmatron with a moving mechanism, characterized in that before the input to the microwave plasmatron is equipped with a polarizer or microwave input device with rotation of the plane of polarization; a broadband transistor amplifier with a master oscillator is used as a source of microwave energy an electromagnetically adjustable frequency oscillator, between which an electrically controlled attenuator is installed, and to automatically maintain the optimal operating conditions of the microwave plasma torch (resonant mode and the optimum surface temperature of the support tube), a computer with programmed control of the manufacturing process for preparing fiber optic fibers and automatic feedback system with a surface temperature sensor of a quartz tube and a level measurement sensor microwave power reflected from the input of the microwave plasma torch.

The diagram and the relationship of the main nodes of the proposed device is presented in figure 2.

The device proposed in this invention consists of a low-power master oscillator 1, electrically tunable in frequency, electrically controlled attenuator 2, transistor broadband amplifier 3, ferrite circulator (valve) 4 with a level control sensor reflected from the input of the microwave plasma torch resonator microwave power, round (flexible corrugated) of the waveguide or coaxial cable 5, the polarizer _11, the TE wave (H ₁₁₎ or, preferably, microwave radiation into the resonator of the input device with the rotation of the polarization plane uu 6, the microwave plasma torch cavity on the type of vibrations the TE ₁₁₁ (N ₁₁₁₎ 7 with a quartz supporting tube 8 disposed coaxially with the axis of the microwave plasma torch, furnace 9 for heating the reference quartz pipe system for moving the resonator 10, a vacuum system 11, flow system chemical reagents and oxygen 12, an oxygen dehydration unit 13, two vacuum gauges 14 located at the inlet and outlet of the support pipe, leakage 15 and trap 16 before the exhaust gas enters the pump, an automatic feedback system consisting of a level control sensor reflected from input yes resonator (microwave plasmatron) microwave power 4 and sensor control support tube temperature 17, an electrically controllable attenuator 2 and electrically tunable oscillator 1, which via the computer 18 automatically provide a resonant mode of the microwave plasma torch 7 on the type of vibrations the TE _{111 (111} N) and a constant, optimal for a given mode of deposition, the temperature of the supporting surface of the quartz tube 8 at various speeds move the microwave plasma torch, when changing the working gas pressure, concentration ii chemicals and their flow rate.

The order of the device.

The work begins with pumping out the support pipe, turning on the furnace and supplying a mixture of O ₂ and SF ₆ to the support pipe. Using a hydrogen-oxygen burner, the pipe is heated to a softening temperature. Then the burner is removed, the furnace is lowered and the heating is turned on, the pipe is sealed and vacuum. This is followed by the inclusion of a microwave generator, ignition of a discharge in a microwave plasmatron (resonator), and the inclusion of a system of microwave plasma-chemical soft etching and polishing of the inner surface of the support pipe.

After the furnace reaches the set temperature, the supply of reagents is turned on according to the program set in the computer and the process of deposition of quartz glass doped with fluorine, germanium and various rare-earth metals is carried out to obtain the required refractive index profile. At the end of the deposition process, the furnace rises, the pressure in the support pipe rises to atmospheric pressure, a hydrogen-oxygen burner is supplied to the pipe, and the process of collapse of the tubular billet is performed.

All technological parameters of the process (temperature, pressure, consumption and concentration of reagents, power of the microwave generator) are regulated and monitored through a computer using sensors and are changed according to a given program. The device allows to obtain blanks with a greater depth of the depressed fluorosilicate cladding equal to Δn = -2.5%, the absence of a central dip in the core of the SiO ₂ / SiO ₂ -F fibers, providing the optical fibers with low optical losses, numerical aperture NA = 0.33, weak sensitivity to bending without increasing Rayleigh scattering at λ ₀ = 1.3 μm and high dispersion (transfer) characteristics of optical fibers (OVS).

Table The results of doping the quartz core of the workpiece with various rare-earth compounds №№ pp The original connection REM Optical characteristics of optical fibers (attenuation, dB / km at λ = 1.3 μm) one ErA ₃ Phen 0.5 2 NdCl ₂ 6H ₂ O 0.6 3 YbA ₃ Phen 0.55

Claims (6)

1. A method of manufacturing preforms of single-mode and multimode W-type optical fibers by plasma-chemical deposition of a deeply depressed fluorosilicate cladding SiO ₂ -F and a silica core SiO ₂ with Δn equal to -2.5% using a “cold” nonequilibrium, uniformly ionized microwave plasma of a reduced pressure on the inner surface of the optically clean supporting quartz tube, the surface of which is preliminarily subjected to chemical, fire and microwave plasma-chemical treatment, and then subsequently served at temperatures 1050 ° C inside the tube in a microwave discharge gas mixture of O ₂ and SiCl ₄ + C ₃ F ₈ to form a reflecting shell, and at a temperature of 1200 ° C - a mixture of SiCl ₄ + O ₂ gas to form a core preform during the reciprocating movement of the microwave -plasma with a TE ₁₁₁ (H ₁₁₁ ) resonator along the pipe at a speed of 2.0-3.5 m / min and rotation of the supporting quartz pipe at a speed of 0.5-1 rpm. 2. The method according to claim 1, in which the quartz core of the preforms of W-type optical fibers is alloyed with germanium and fluorine. 3. The method according to claim 1, in which the quartz core of the preforms of W-type optical fibers is alloyed with various rare-earth metals from the group consisting of neodymium, erbium, ytterbium, and additives to them selected from the group consisting of potassium, aluminum, phosphorus, germanium, nitrogen, fluorine, both individually and in various combinations, and volatile compounds of rare-earth metals, mainly organometallic compounds with high vapor pressure, are used as starting reagents. 4. The method according to claim 1, in which when forming a reflective sheath as a fluorine-containing compound, Freon C ₃ F _{8 is used} . 5. A device comprising a furnace, a quartz support tube located therein, a vapor-gas mixture supply system, a vacuum system, a microwave generator and a microwave plasmatron with a moving mechanism, characterized in that a polarizer or microwave radiation input device is installed in front of the plasmatron entrance with by rotating the polarization plane, a broadband transistor amplifier with a master oscillator electrically tunable in frequency, between which an electrically controlled attenuator is installed, is used as a source of microwave energy I automatically maintain optimal operating conditions of the microwave plasma torch device comprises computer controlled manufacturing process the preforms of optical fibers, and an automatic system with feedback sensor reference surface temperature of the quartz tube and the sensor measuring the level reflected by the resonator input microwave power. 6. The workpiece obtained according to claims 1 to 4, with a deeply depressed fluorosilicate shell SiO ₂ -F with Δn equal to 2.5%.

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