Optical fiber with low loss at the wavelength of 1385 nm, the manufacturing method and the multi-channel system that uses such an optical fiber

 

(57) Abstract:

The core single-mode fiber manufactured by the method of axial deposition from the vapor phase. The ratio of the diameter of the outer shell to the diameter of the core of this rod does not exceed 7.5. The core with the core dehydrated in chlorine - or fluoride-containing atmosphere at a temperature of about 1200oC to reduce the concentration of ions IT to a value less 0,8 wt.h./billion, and then cured in a helium atmosphere at a temperature of approximately 1500oC: the transformation of porous, consisting of particulate matter mass in the glass. Hardened rod is extended using an oxygen-hydrogen burner with the formation on its surface a layer of ions of HE, the bulk of which is then removed from the surface of the core in the process of plasma etching. After etching the core with the core placed in a glass tube with a low content of IT. After compression of the tube on the rod turns the workpiece. The block is pulled optical fiber to which is applied one or more protective coatings. The method is suitable for the manufacture of fibers with low content of IT. Losses in the fiber on the wave of 1385 nm is reduced to a level smaller losses of NGOs 1600 nm. The possibility of using such a fiber creates conditions for the creation of multichannel systems using wavelength division multiplexing, capable of transmitting optical signals over distances exceeding 10 km 4 s and 8 s.p. f-crystals, 9 Il.

The invention relates to a single-mode optical fibers, in particular for manufacturing optical fiber with the desired characteristics of the transmittance around the wavelength interval from 1200 to 1600 nanometers (nm).

The optical loss in the fiber depend on the purity of the glass and are characterized by the weakening of the light from the input end of the fiber to its output end. The smaller the loss, the greater the distance light can pass before it will need to be strengthened. Especially low loss glass has in the wavelength range from 1200 to 1600 nm, and therefore, for many years the transmission of light waves is bounded by the regions of wavelengths 1310 nm and 1550 nm. For reasons that limit the transmission of light in these spectral regions, are loss during bending of the fiber at wavelengths above 1600 nm, the amplitude characteristic of the existing optical amplifiers, Rayleigh scattering and absorption of light hydroxyl ions (OH), which occurs in a narrow wavelength range around there are still "white spots". However, from the point of view of physics to solve this problem, there are no fundamental obstacles, because the use of the materials on the basis of indium phosphide (InP) allows you to create sources of light throughout the wavelength range from 1200 to 1600 nm. In fact, in recent times many issledovatelyami were developed lasers that work on different wavelengths in this range and which are specially designed to study the absorption of light not only in the fiber, but in the conditions of the polluted atmosphere. In addition to these lasers were created and fiber laser pumping, creating radiation with a wavelength of 1480 nm.

In Fig. 1 shows the dependence of the total losses in an optical fiber with a glass core. Curve losses built in the wavelength range in which the total losses are small enough to allow the work of the real optical communication systems. In this wavelength range loss is determined mainly Rayleigh scattering and absorption of ions IT.

The nature of Rayleigh scattering associated with irregular density distribution and composition of the material on the fiber. Such changes in the density and composition of the fiber occur in the manufacture of glass, co transition. There is a certain level of thermal perturbations arising in the transition point, which is the cause of thermal fluctuations and changes in the composition of the glass, which is "fixed" in the crystal lattice when the softening temperature and depend on the composition of the material. The size of such defects in the glass is less than the wavelength of light. The presence of such defects is determined by the nature of the glass and eliminate them it is impossible, in consequence of which they define the lower boundary of the losses in the fiber. Rayleigh scattering is proportional to 1/4, where is the wavelength of light.

Optical loss on the wave of 1385 nm is determined by the amount of water remaining in the glass. The more water in the glass, the higher the loss. Therefore, the light absorption of hydroxyl ions is often seen as the absorption of light "water," which is associated with the energy of light radiation absorbed by the ion IT on the wavelength, which is determined by its various waveforms. For example, two main types of oscillations of this ion occurs at wavelengths 2730 nm and 6250 nm and correspond to the longitudinal and transverse oscillations. However, higher harmonics and combinatorial frequency significantly affect light loss near infrared and the mid-wave band, which in the future should work optical fiber communication systems. Therefore, such losses associated with the vibrations of hydroxyl ions at this frequency, it is highly desirable to reduce and bring to the maximum possible minimum level. Unfortunately, even a very small content of HE ions at the level of one part per million calls at a wavelength of 1385 nm loss greater than 65 dB/km At all desire to reduce the concentration of ions IT to the level of 0.8 ppm billion, in which the total light loss on the wave of 1385 nm would be comparable to the total loss on the wave 1310 nm (which account for about 0.33 dB/km), it was considered almost impossible for purely economic reasons. With such a concentration of ions IT is associated with their loss should increase losses from Rayleigh scattering at a wavelength of 1385 nm 0.05 dB/km, providing the amount of the total losses at a level close to that of 0.33 dB/km

In Fig. 1 shows the three "Windows", each of which covers a specific range of wavelengths in which the normal operation of the optical fiber. Historically earlier fiber system worked near the wavelength of 825 nm (the first window), because in 1979 appeared running on Windows, was used from 1980 to 1983, and later, starting in 1986, began to create systems operating in the wavelength range close to 1550 nm. In the future intended for the transmission of light waves in optical systems with limited due to the presence of water loss at 1385 nm is available for widespread use of optical fiber should be effective throughout the range of wavelengths from 1200 to 1600 nm.

In multimode fibers waves are transmitted primarily through the core due to the relatively large difference of refractive indices of the core and covering it and is made in the form of a coating shell. As in multimode fibers passing waves is essentially limited by the fiber core, the presence of HE ions in the outer shell of fiber does not have a significant impact on light loss fiber. Were made and described in the literature multimode fiber with low absorption of light HE ions in the region of wavelength of 1385 nm (see, for example, Moriyama and others, "Ultimately Low HE Content V. A. D. Optical Fibres", Electronics Letters dated August 28, 1980 , volume 18, No. 18, pp. 698-699). Currently, however, there is a need in the manufacture of single-mode fiber with the transfer of a significant part of energy is="ptx2">

In August 1986 in the journal of Lightwave Technology, vol LT-4, No. 8, pp. 1026-1033 published an article N. Murata entitled "Recent Developments in Vapor Phase Axial Deposition", which contains information about single-mode optical fiber with low loss at a wavelength of 1385 nm, due to absorption of light by water. In this fiber, however, the low absorption of light by water is ensured by the fact that before applying the outer coating of silicon oxide on the fibers previously in large numbers is applied to the intermediate coating. (The process of axial deposition from the vapor phase or VAD process is inherently very expensive process and therefore any reduction in performance may so increase the cost of fiber that application in a large number of intermediate cover is simply unacceptable for mass production of fiber.) The numeric index of the fiber (D/d), known as the ratio of the coating/core, is determined by the ratio of the diameter (D) core diameter (d) of the core, and in the best case scenario, this dimensionless quantity should be as small as the amount applied in the form of a coating material is proportional to (D/d)2. In article Murata described in is the actual content of IT before applying the outer coating of silicon dioxide the ratio of the coating/core must exceed 7.5. This value is a numeric index of D/d is unacceptably large. However, it is advisable to obtain a Central core of fibers with a small content of IT, in which the ratio D/d is less than 7.5.

In U.S. patent 5397372 March 14, 1995, describes an improved method of chemical vapour deposition (MCVD-way) used for manufacturing optical fiber with low content of IT. In this patent for a coating of a material with high refractive index on the inner surface of the glass tube is proposed to use hydrogen-free plasma torch. Around the core fiber is crimped tube made of glass, resulting in a billet, which during the subsequent extraction is possible to obtain only a relatively short fiber length of about 0.7 km). For long fibers on an industrial scale, as is obvious, the workpiece must have a greater length. It should be noted that the known technology of manufacturing of long workpieces, which is based on the production of the prisoner in the pipe stem, is very economical, however, without solving the serious problems associated with pollution fiber ions IT.

The problem is, the cat is th data transmission over large distances in the wavelength range from 1360 to 1430 nm. Another equally important problem to be solved is the creation of a single-mode optical fiber with low peak losses due to the presence of water on the wave length of 1385 nm and develop cost-effective method for industrial production of such fibers.

The process of manufacturing a single-mode optical fiber with low light losses on the wave of 1385 nm begins with a stage of forming a glass rod with a core refractive index greater than the refractive index of the layer deposited on her shell. The core diameter is denoted by (d), and the diameter of the besieged her shell is denoted by (D). The ratio of sheath/core this core with a core of less than 7.5, and the concentration of ions IT is less than 0.8 wt.h./billion To the premises in a hollow glass tube with a correspondingly low concentration of ions of HE core with the core extends. Under the influence of heat from the tube placed in her by the rod is heated and compressed around the rod. The resulting product is a billet, which is then made fibre.

This blank is placed in an oven and pull one end, receiving from her glass. Steklovary exposed to radiation.

In one embodiment of the invention the core with the core legarrette GE, and is produced by the axial vapor deposition (VAD method). Ready rod with core dehydrated in an atmosphere containing chlorine or fluorine, at a temperature below 1300oC, and then hardens in a helium atmosphere at temperatures above 1400oC. thereafter, etching is carried out rod, using hydrogen-free plasma torch, in which the surface of the rod removes a small amount of material.

In one embodiment of the invention the extractor rod with a core by using an oxygen-hydrogen burner, the application of which requires subsequent etching to remove from the surface of the rod polluting it HE ions, which are formed therein during extrusion with the use of such burners. In another embodiment of the invention the extractor rod with a core is carried out using a hydrogen-free plasma torch, which does not contaminate the surface of the rod and therefore does not require a subsequent etching of the rod.

By the present invention for the first time confirmed the possibility of industrial production of optical fibers with piracy, still in this order still has not been merged into one process. Despite the long existing need in the using wavelength range from 1200 to 1600 nm for optical data transmission and the availability of a whole number that appears in the early 1980s publications conducted "outstanding" experiments, indicating the possibility of manufacturing optical fiber with low content of IT, but so far, these fibers on an industrial scale still has not been released.

The invention and variations in its implementation are examined in more detail in the description below, with reference to the accompanying drawings on which is shown:

in Fig. 1 - range of total loss of an optical fiber, which shows the spectral region at which the energy is absorbed by ions of HE,

in Fig. 2 is a diagram illustrating the manufacture of the core with the core method axial deposition from the vapor phase,

in Fig. 3 is a block diagram of the proposed invention, a method of manufacturing optical fibers,

in Fig. 4 is a schematic representation of a plasma torch that is designed to remove ions from a surface of the core with the core

in Fig. 6 is a cross section proposed in the invention of glass blanks, which shows the dimensions of the core and shell of the rod,

in Fig. 7 is a representation of an optical fiber, extruded shown in Fig. 6 glass blanks, with two layers of protective coating,

in Fig. 8 is a graph which shows the measured transmittance characteristic of the optical fiber manufactured proposed in the invention method, and

in Fig. 9 is a diagram of four-channel system with wavelength division multiplexing for transmission lines operating in the wavelength range from 1360 to 1430 nm.

In Fig. 3 shows a block diagram of the proposed in the present invention, a method of manufacturing optical fiber with low loss on the wave of 1385 nm. The individual stages of the method are indicated by positions (31 - 38), which are stored in the entire description. The first three stages (position 31-33) belong to the manufacturing of the core with a core with a low content of IT (less than 0,8 frequent./billion), which is then covered by an outer shell of a glass tube. These first three stages, in principle, can be replaced with one stage of formation of the core with the core, in which the ratio of the obtained deposition oblock ergene with the core is made following the method of axial vapour deposition (VAD method), which is the block diagram indicated by the position 31.

Schematic diagram of the method of axial deposition from the vapor phase, consisting in the deposition to form the core of silica glass particles or "soot", shown in Fig. 2. The rod 20 is composed of the core 21 and deposited on her shell 22, which has a refractive index less than that of the core. It is known that the light beam is deflected in the direction of the field fiber, which has a relatively large refractive index, and on the basis of this law of physics, the movement of light in the fiber occurs along its center. To create in the fiber region with a relatively high refractive index is used burner 201, which is supplied fuel (in particular, oxygen and hydrogen) and source material (in particular, GeCl4and SiCl4and which is accompanied by formation directed towards the center glass rod of flame, which contains pairs of source material. Contained in the flame source material reacts and of the deposited glass particles (soot) forms the core 20. The rod is usually elongated in the vertical direction and in the beginning of deposited particles form the upper end wiped the rotatin around its axis, resulting in the deposition of particles occurs uniformly throughout its length and throughout its circumference. Another burner 202 is used for formation of the core 21 and the layer 22 of glass, called received by the deposition of the shell. Used in the burner 202 to education caused by the deposition of the shell 22, the source material is, for example, SiCl4. It should be noted that the doping of the core 21 GE is one of the ways to create a core with a higher in comparison with the shell refractive index. In another embodiment for manufacturing the core, you can use SiCl4as source material, and doping shell fluorine will give the refractive index of the cladding is less than that of the core. In this case, the burner 202 together with SiCl4served SF6, CCl2F2, CF4. Detailed description of the various methods of making fiber described in Chapter 4 of the book Optical Fiber Telecommunications II. Academic Press, Inc., 1988, AT&T and Bell Communications Research, Inc. In particular, in section 4.4.4 of this book (pp. 169-180), which is incorporated in this description by reference, describes a method of manufacturing fibers, based on the process of axial deposition from the vapor phase.

In made OPIC diameter (d) of the conductors is less than 7.5. Because the process of axial deposition from the vapor phase is an expensive process, any cost savings in the manufacture of the core with the core directly will reduce the cost of fiber. It is known that the amount deposited from the vapor phase of the material required to manufacture the core with the core proportional to (D/d)2. However, when the decrease of the ratio D/d increase requirements to the purity of the outer tube. The reduction of D/d leads to an increase in optical power transmitted through the outer tube of the fiber, and therefore the presence of such impurities as ions IT causes additional losses associated with the light absorption of these ions. This is due to the mobility of ions IT and their migration in the direction of the core, which is particularly intensive in the process of fiber extraction. Even more dangerous is the possibility of decomposition of HE ions and the formation of the hydrogen gas, which has higher mobility than ions IT, and which can diffuse during drawing of the fiber into its heart. Subsequent interaction between hydrogen and atomic defects in the fiber core are formed in it HE ions. Fiber with a core with Seny to have the outer tube with an unusually low content of IT, the cost of which is currently quite high. So we produced for industrial purposes fibre ratio (D/d) diameter caused by the deposition of the coating to the core diameter should be in the range of 2.0 to 7.5.

At the stage indicated in Fig. 3 position 32 is dehydration rod with a core that is placed in a chlorine - or fluorine-containing atmosphere to a temperature of about 1200oC. At this stage the core with the core has a fine porous structure, and chlorine gas, for example, easily passes between soot particles and ions replaces IT chlorine ions, providing almost complete dehydration of the rod. The rate of substitution ion IT depends on the flow rate of chlorine gas and the temperature of dehydration.

At the stage indicated in Fig. 3 position 33 is cured rod with a core that is placed in a helium atmosphere with a temperature of about 1500oC. Curing is an operation during which a porous, consisting of fine particles of the rod turns into a dense glass, in which there are no boundaries between the individual particles. Detailed description of the processes of dehydration and otvergli.

At stage 34 of Fig. 3 using an oxygen-hydrogen burner is the elongation of the rod with the core. On this stage burner is the most optimal from the point of view of cost method of allocating a large amount of heat that is required to pull the rod. In another embodiment, at this stage, as described below, it is possible to use hydrogen-free plasma burner, eliminating the etching operation rod (indicated by item 35). Usually the rods with a core produced from axial deposition from the vapor phase, have too large size for enclosing them in with regular dimensions of the outer tube, and therefore before to reduce their diameter, they are usually subjected to elongation, during which there is a reduction in their diameter. The elongation of the rod is performed on the normal, intended for drawing glass machine, the construction of which is well known. Core with a core set between the front and rear pasterns of the machine and is put into rotation. During rotation along the rod at a constant speed in the direction of the front of the headstock is moved beneath the core of the burner. Simultaneously with the movement of the burner saddah gases, in particular, hydrogen and oxygen in the burner is about 30 and 15 l/min, respectively. When used for heating rod conventional industrial hydrogen on the surface of the core with the core layer is formed IT. The process of lengthening rod with a core of well known and are described, for example, in U.S. patent 4578101 dated March 25, 1986

In Fig. 3 position 35 marked the etching stage of the elongated rod, which is carried out preferably using hydrogen-free plasma torch. In Fig. 4 schematically shows a device for plasma etching with the core rod 20, in which the surface of the rod is removed the main part of the HE ions. Detailed information about the plasma etching can be found in U.S. patent 5000771 dated March 19, 1991, which is incorporated in this description by reference. Description of the main features of the process of plasma etching below, although it is clear that for effective removal from the surface of the rod ions IT is possible to use other methods. Such is not limiting the invention methods include mechanical grinding and chemical etching.

For rapid etching or clear the ü isothermal plasma. Using creating an isothermal plasma torch predominant mechanism of surface removal of a substance is its evaporation, due to the high plasma temperature, which is in the center of the plasma usually exceeds 9000oC. during contact with a conductive plasma ball with refractory dielectric surface of the rod is an intensive transfer to it the energy of the plasma and an increase in the surface temperature of the rod above the temperature of evaporation is located on the surface of the dielectric material.

In Fig. 4 schematically shows a device for plasma etching. The burner 10 includes a casing 11 in which is molten silicon dioxide and which is connected to the source 18 of the gas tube 16 and from another source 17 other gas tube 15. The gas coming from the source 17, is a gas used for the plasma discharge inside located in the casing 11 of the screen 110. For the plasma ball 12 is used high-frequency coil 19 and the generator 14 high frequency. The gas sources are used to supply the burner is spent on maintaining a plasma of an ionisable gas and education inside the nozzle n is ω ionization of the main part of the plasma ball is located outside the burner. The added gas from source 18 is fed at the top button around the screen 110 part of the burner, in which for the conversion of gases under the action of energy of a high frequency field in the plasma is required to provide a relatively large power consumption. Usually located outside of the burner part of the plasma ball is less than 50% of the total volume generated in the plasma burner as to create a stable plasma to the center remained inside the nozzle, which ensures a steady supply to the plasma from a source of high frequency energy sufficient to maintain its steady state. In addition, in the case when located outside of the burner part of the plasma ball is from 30 to 50% of the total volume of plasma, a source of high frequency energy should have more power, and the gas flow necessary to create a stable plasma must also be greater than in the case when this part of the plasma ball is less than 30% of the total volume of plasma. Shifting the center of the plasma to the output end of the burner, you can easily ensure the impact of the plasma on located under the burner with the core rod 20. It is obvious that the large part of the plasma ball will be located EXT is selected on the machine 120, which causes it to rotate. In principle, all devices for the installation of such cores on the machine and rotation are well known to specialists in this field of technology. During uniform rotation of a cylindrical rod and a simultaneous corresponding movement along the core of the plasma torch stem material 20 is removed from its entire surface with preservation of the cross-sectional shape of the rod. The principal is that this method of etching allows you to remove from the surface of the rod HE ions. In a preferred embodiment of the invention, the depth of etching is 0,250,15) mm and the diameter of the rod, equal to plasma etching of approximately 20 mm, is reduced after etching to approximately 19.5 mm

The gas flow in a plasma burner (O2or preferably ABOUT2/Ar) is from 1.0 to 100 l/min Plasma ball formed under the action of the field created by the high-frequency generator, which is typically at a frequency of 3 MHz consumes power from 20 to 40 kW, is moved relative to the rod with a speed of from 0.01 to 100 cm/s over the entire area of the processed rod length of about 1 m, the Speed of rotation of the rod typically is in the range from 0.1 to 200 rpm Intension can be reduced through the use of large external pipes. Preferably the tube to run from synthetic silicon dioxide, which is well known in the art and widely used due to its high purity, low attenuation coefficient and high tensile strength. From the purity of the outer tube depends on the distance from the core of the fiber. At the stage indicated by the position 36, the terminal with the core placed in a tube of glass with a low content of IT, it should be noted that the smaller the ratio D/d, the cleaner must be the tube (i.e., the lower should be the content of IT). As an example we can cite the following table, in which for different values of the ratio D/d are recommended for the implementation of the present invention different levels of content in the outer tube:

D/d is the Concentration of HE, frequent./million

7,5 - < 200

5,2 - < 1,0

4,4 - < 0,5

At the stage indicated in Fig. 3 position 37, is the compression of the glass tube on the web with the core and receiving the workpiece fiber. The way this operation is illustrated in Fig. 5. In Fig. 5 shows the machine 500, which has a core rod 20 is placed inside the hollow glass tube 40, which is crimped to the terminal. As shown in Fig.sebaceous hinge, mounted in a holder 53, which is attached to the lower cantilever support 55 of the vertical frame 510 of the machine and can be rotated at the hinge of the Chuck in either direction relative to the machine body. The lower cartridge 52 has a seal that seals the outer surface of the tube 40. The rod 20 is suspended from the upper cartridge 51 coaxially with him. The cartridge 51 is fixed on the upper support surface 56, which is cantilevered relative to the frame 510 of the machine. The lower and upper bearings 55 and 56 are arranged in a certain way relative to each other and determine the relative position of the tube and rod, the main part of the length of which is located inside the tube.

During operation it is necessary to control the gap between the outer surface of the rod 20 and the inner surface of the tube 40. In particular, for a rod with an outer diameter of 20 mm is necessary to use a tube with an inner diameter of 21.5 mm, which allows to provide between them a uniform gap of 0.75 mm, the location of the rod in the center of the tube is preferred, but not always achievable when it is installed, and therefore sometimes to the compression tube rod in several places refers to a tube or is located in her eccentric. If after compression tube workpiece is displaced relative to the center rod. For the reduction of the eccentricity of the tube can accordingly be moved using a universal joint located at the bottom of the frame 510, which allows you to rotate the tube in any direction.

The tube 40 is located inside the annular burner 520, which can be used oxy-hydrogen burner. When turning the tube 40 and the rod 20 around their longitudinal axes burner 520 heats the tube 40 to a temperature at which the tube position is changing by itself and stop the motion of the burner tube is displaced and can be centered relative to the rod. This is due to the fact that when heated tube in its particular place reduced operating voltage, and the tube itself can be centered relative to the rod 20. At the upper end 41 of the tube burner 520 within a certain period of time remains fixed and, when melted, forms at this point of the rod 20 tight seal. At this point, using the source 530 vacuum, which is connected with the lower end of the tube passing through the cantilever support 55 and the holder tube 53 531, the pressure inside the tube is reduced and becomes less than the external pressure. Below is the end. Typically, the pressure inside the tube is maintained at 0.2 ATM. After the appropriate shutter speed burner 520 goes down and moves along the tube. As the movement of the burner along the tube 40 within the latter is supported by an appropriate vacuum, and its length in the heating zone is gradually increased, and the tube is relatively fast, is compressed by the rod 20, forming the blank for the manufacture of fibers, the cross section of which is shown in Fig. 6. A more detailed description of this process can be found in U.S. patent 4820322 dated April 11, 1989, which is incorporated in this description by reference. In another embodiment for the compression tube on the web with the core you can use the plasma torch, which further reduces the content of IT, as described in U.S. patent 5578106 dated November 6, 1996, the Removal of the layer IT with the outer surface obitaemoj around the rod outer tube is not necessary, because this layer is located far enough from the core. As an example, the following dimensions of workpiece: 100 cm (length), 63 mm (the diameter of the outer tube), 19 mm (outer diameter fabricated by deposition of a rod) and 4.5 mm (core diameter). Accordingly, the ratio D/d in this piece Rav is ahatovici. In the manufacture of optical fiber glass preform is suspended vertically and a controlled velocity move in the oven. In the furnace, the preform is softened, and from its molten end use driven in rotation of the exhaust roller, located in the lower part of the extraction column, freely drawn optical fiber. Because of the abrasive action on the surface of the fiberglass may cause defects on the fiber immediately after extrusion before contact with any surface it is necessary to apply the coating. To avoid damage to the surface of the optical fiber while applying the coating, the latter is applied to the fiber in liquid form. Applied to the fiberglass floor should harden faster than the fiber with the coating reaches the exhaust roller. The curing of the coating is within defined process fototerapia period of time, i.e. the process by which a liquid coating material becomes solid when exposed to a radiation source.

In Fig. 7 shows proposed in the present invention elongated optical fiber 700 with double coating. This fiber has two coating layer on stretches the tube 73. The fiber 70 has a diameter of about 125 μm. It should be noted that the ratio of the size of the workpiece 60, shown in Fig. 6, corresponds to the ratio of the stretched fiber 70. (Despite the fact that the diameter of the extruded fibers are thousands of times smaller than the diameter of the workpiece, the profile of the refractive index have the same!). First on the fiber 70 is applied to the inner layer 75 protective coating (first coating), and then to the surface of the first coating applied to the outer layer 76 (second floor) of the protective coating. For the application of both coatings are polymeric materials, acrylic-based, having a specified hardness values. The material of the second coating, which is external and which are in contact when working with fiber typically has a higher modulus of elasticity (in particular, 109PA), whereas the material of the first coating, which serves as a kind of spacer that reduces losses due microthiol has a relatively small modulus of elasticity (in particular, 106PA). The second coating can be applied to the first in that moment, when the first coating is in a wet state, while simultaneously curing both coating effects on Nasca characteristic losses is made in accordance with the invention an optical fiber. The maximum measured value losses in the region of the wave length of 1385 nm is less 0,29 dB/km, which corresponds to the set of the invention the purposes and less than the measured losses (of 0.33 dB/km) on the wave of 1310 nm.

In Fig. 9 shows the scheme proposed in the invention operating in the mode spectral multiplexing system 90. In this system there are four transmitter 81-84, which in the wavelength range of 1200-1600 nm produce four modulated wave with a given length and four different frequency bands. At least one of the transmitters (in particular, 81) works on the wave length of which lies in the range 1360-1430 nm. Still work in this "unexplored" range when the optical signal transmission over long distances (in particular, at distances over 10 km) it was considered impossible because of the large losses associated with absorption of the signal energy HE ions. The modulated waves are then combined in a device for sealing or signal in the multiplexer 85 and fed into the optical cable 900, the design of which is well known in the art and described in many publications. In this system, the cable 900 includes one or more fibers, including a single-mode optical fiber 700, which is the wavelength range from 1200 to 1600 nm, with the wave of 1385 nm loss smaller than the wave of 1310 nm. On the receiving end of the system four channels are separated according to their lengths by using the device for separation of the channels, or the demultiplexer 85, and enter the receivers 91-94, allowing to receive signals with different frequency bands. In on the area between the multiplexer 85 and demultiplexer 95 can include not shown in the diagram optical amplifiers. In the considered system, the multiplexer and demultiplexer are passive optical scheme.

In the above specific options within the basic idea of the invention it is possible to make various changes and improvements, such as the manufacture of the core with the core not by the method of axial deposition from the vapor phase, and the other suitable for this purpose way.

1. A method of manufacturing a single-mode optical fiber (700), which is characterized by low loss at the wavelength of 1385 nm, namely, that the method of deposition of soot form a glass rod (20) has a cylindrical core (21) diameter (d) with a deposited deposition of the shell (22) diameter (D) ratio D/d is less than 7.5, then the glass rod on the ones HE up to a level of less than 0.8 wt. am/bn, then the glass rod utverjdayut at temperatures above 1400°C, prepare a hollow cylindrical tube (40), the inner diameter of which is somewhat larger outer diameter of the glass rod and which is made of glass with a content of ions IT is less than 200 wt.h./million, then a significant part of the glass rod is placed inside a specified of a hollow tube, then the tube is affected source (520) of heat that move in the axial direction along the tube and rod and which when exposed tube shrinks and compresses inside the rod, forming together with it a glass workpiece (60), and then from the glass billet pull the fiberglass (70).

2. The method according to p. 1, in which the elongated fiberglass (70) put the material forming on the glass protective coating (75, 76), and then a protective coating is exposed to a radiation source for curing the material of this protective coating with the formation of the optical fiber (700).

3. The method according to p. 1, in which the glass rod is lengthened by using a source of heat, which when exposed surface of the rod is contaminated with ions of HE, and then remove the HE ions with the surface is ametra rod by a specified amount.

4. The method according to p. 1, in which the ratio D/d is more than 2.0 and less than 7.5.

5. The method according to p. 3, in which the glass rod (20) extend using an oxygen-hydrogen burner.

6. The method according to p. 3, in which HE ions are removed from the surface of the elongated glass rod (20) with the use of hydrogen-free plasma torch (10).

7. The method according to p. 1, in which the soot deposition process used method of axial deposition from the vapor phase.

8. The method according to p. 1, in which the core (21) doped with germanium.

9. The method according to p. 1, which is obtained by precipitation of the shell (22) doped with fluorine.

10. Glass workpiece (60) manufactured by the method according to p. 1.

11. Fiberglass (70), drawn from a glass preform (60) under item 10.

12. Multi-channel system (90) with wavelength division multiplexing with multiple sources (81-84) optical signals modulated at different wavelengths in the range of 1200-1600 nm, at least one of these sources work on the wave lying in the range 1360-1430 nm, the device (85) seal of optical signals, located at the entrance of multichannel systems using wavelength division multiplexing device (95) rasuplotnenie transmission, which connects the sealing device with the decompression device and the length of which exceeds 10 km, while in the specified transmission line includes an optical fiber (700), whose loss at the wavelength of 1385 nm is less than the loss at the wavelength of 1310 nm and which is made of a rod (20) with the core, encased in a glass tube (40) with the content of ions IT is less than 200 hours/million, with the specified terminal with the core content of HE ions is less than 0.8 h/bn, and the ratio D/d is obtained by deposition of the shell and the core is less than 7.5, where (d) is the diameter of the core (21), a (D) is the diameter obtained by the deposition of the shell (22).

 

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The invention relates to a device for transmitting optical data and, in particular, to a device for implementing redundancy in the transmission of optical data

The invention relates to a transceiver system that uses light waves, and can be used to transfer information between peers through the atmosphere

The invention relates to a single-mode optical waveguide fiber designed for use in communication systems long-haul high-speed transmission, operating in the wavelength range from approximately 1500 to 1600 nm

The invention relates to a single-mode optical waveguide fiber, which has a wavelength zero dispersion shifted in the range of about 1550 nm, a large effective area and low slope full dispersion

The invention relates to a single-mode optical waveguide fiber with a large effective area (aefffor communication equipment

The invention relates to a single-mode optical fiber with a controlled negative full dispersion and a relatively large effective area

The invention relates to a single-mode optical waveguide fiber with a large effective area of Aefffor use in the field of communications

The invention relates to a light guide fiber, designed for long-distance communication systems with high data transfer speed

The invention relates to optical fiber having a core, a deposited coating of a single layer or laminated layers of synthetic material and colour marking on the outer layer of synthetic material or embedded in this layer
The invention relates to fiber optical fibers as the transmission medium for communication systems

The invention relates to the field of fiber optics and can be used in optical communication lines, as well as in the design of physical quantity sensors (optic pressure sensors, temperature, gyroscopes and t

The invention relates to a method and apparatus for manufacturing optical fibers, and more specifically to a method and apparatus for optical fibers doped with erbium, which is used as an optical amplifier, allowing you to increase directly by optical signals, and the method and the device allow to reduce production time while increasing productivity

The invention relates to optical fiber, in particular to the procurement of the fibre, capable of preventing deterioration of the optical characteristics of the optical fiber, which is possible in the manufacturing process of the workpiece single-mode optical fiber and making extracts from it, and to increase the efficiency of passage of the optical signal, and the method of production of this piece
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