Optical fiber with dispersion shifted

 

The invention is used in fiber-optic communication lines (FOCL). Single-mode optical fiber has a Central part of the core, the second part around a Central core, the refractive index of which is less than that of the Central part of the core, and located around the second part of the core shell with a refractive index smaller than that of the second part of the core. In the wavelength range 1490-1625 nm chromatic dispersion of the fiber is 0.5 to -8,0 PS/(kmnm) or +0.05 to +10,0 PS/(kmnm), the effective area of the core is 45-90 μm2the slope of the dispersion is in the range of 0.05 to 0.14 PS/(kmnm2). The bending loss of 100 dB/m or less. 18 C.p. f-crystals, 10 ill., 9 table.

The invention relates to optical fiber dispersion-shifted, which has a large effective area of the core and a low dispersion slope.

The basis of the present invention are used patents registered in Japan (Japanese patent application H11-212949/1999, Japanese patent application H11-230137/1999, Japanese patent application 2000-64008, Japanese patent application 2000-224491 and Japanese application paten is.

In the long-distance communication, such as repeater transmission system with optical amplifiers, which uses fiber-optic amplifiers, an important feature is the reduction of nonlinear optical effects. The parameter called nonlinear optical coefficient serves as a measure of the degree of a nonlinear optical effect. Nonlinear optical coefficient is expressed by the ratio n2/Aeffwhere n2 is the nonlinear refractive index and aeff- the effective area of the core. The value of n2 remains almost constant and depends mainly on the type of material, an effective method to reduce the nonlinear optical effects is the increase Andeff.

On the other hand, in systems multiplexed transmission separation by wavelength, which allow the transmission of large amounts of information, there is a need to suppress the values of the chromatic dispersion and the reduction of dispersion slope. It is well known that in the multiplexed transmission separation by wavelength, when the bandwidth there is a wavelength at zero dispersion, the transmission quality is declining due to nelineinoi dispersion is accompanied by distortion of the waveform, there is a need to suppress this value up to a certain size. In order to meet these conflicting requirements, we developed an optical fiber, which is called optical fiber non-zero dispersion shifted, in which the value of the chromatic dispersion in the wavelength range control within a narrow range.

In addition, the system multiplexed transmission separation by wavelength important aspect is the reduction of the slope of the dispersion. Under the slope of the dispersion, which shows the dependence of the wavelength on the value of the chromatic dispersion, the mean slope of the curve obtained by the graph, where the horizontal axis represents wavelength (nm) while the vertical axis is the value of the chromatic dispersion (PS/km/nm). In the system multiplexed transmission separation by wavelength, if the slope of the dispersion in the transmission line (optical fiber) is large, then the difference in value of the chromatic dispersion in the range of wavelengths will be significant. For this reason, when considering very large values of the variance, which depends on the wavelength, there are difficulties associated with the transmission quality, which Moi.

Specific values for the required attributes Andeffand dispersion, which are discussed above, will vary depending on the system used. In a system in which the transmission signal is produced at very large distances, such as a system of communication with submarines tend to reduce the nonlinear optical effect resulting from the increase Andeff. On the other hand, in the system, extending from a few tens to a few hundreds of kilometers, sometimes there is a need to suppress the values of dispersion in a wide wavelength range by reducing the slope of the dispersion. In addition, based on the minimum conditions required for the transmission line in the optical communication system, optical fiber must be essentially single-mode, and losses at bends should be maintained at levels up to 100 dB/m or below.

Therefore, in recent times there have been proposed methods of influence to a certain extent on the increase Andeffand reducing the slope of the dispersion with the use of various forms of distribution (refractive index profiles of the refractive index), as, for example, in Japanese laid patent application H10-62640/1998, Japanese laid allow the 0-246830/1998.

In Fig. 10A-10C schematically shows examples of the forms of distribution of refractive index in such optical fiber dispersion-shifted.

In Fig.10A shows one example (step) type core with two forms of distribution of the refractive index, thus formed the core 14, in which position 11 marked the Central part of the core, and a stepped portion 12 of the core is made around its outer periphery, having a lower refractive index than that of the Central part 11 of the core. In addition, around the outer periphery of this core 14 is executed, the shell 17 having a lower refractive index than the stepped portion 12 of the core.

In Japanese laid patent application H8-220362/1996 the present applicant disclosed a solution for smaller diameter to increase Andeffin an optical fiber with an offset variance with the distribution of the refractive index type core dual form.

It is known that with increasing core diameter optical fiber with dispersion shifted and maintaining the similarity of the form of distribution of the refractive index there are two or more solutions in which the value is on, where the characteristics of the wavelength cutoff and losses on the curves are relatively acceptable for practical use, a solution in which the core diameter is relatively small, is called a solution for a smaller diameter, and a solution in which the core diameter is relatively large, is called a solution for the larger diameter.

In Fig.10B shows an example of the form of distribution of the refractive index of the segmented type core, where the core 24 has a configuration with an intermediate part 22 with a low refractive index, which is made around the outer periphery of the Central part 21 of a core with a high refractive index, and with the annular part 23 of the core having a higher refractive index compared with the intermediate part 22, but a lower refractive index compared with the Central part 21 of the core, made around the outer periphery of the intermediate part 22. In addition, around the outer periphery of this annular part 23 of the core made of the first shell 25 having a lower refractive index compared with the intermediate part 22, and around the outer periphery of the first shell 25 is made VCI the refractive index in comparison with the intermediate part 22, thus the configuration of the shell 27.

In addition, in Japanese laid patent application H11-119045/1999 (published) by the present applicant disclosed an optical fiber with dispersion shifted, which is well suited for optical communication systems, in which the decrease of the slope of the dispersion is even more stringent requirement than increase Andeffusing solutions for larger diameter in the segmented type core to form a distribution of refractive index.

In Fig. 10C shows an example of the form of distribution of the refractive index of the O-shaped ring type in which the core 34 has the configuration in the form of a two-layer structure, and the peripheral part 32 of the core with high refractive index is made around the outer periphery of the Central portion 31 of the core with a low refractive index in the center. Around the outer periphery of this core 34 is made shell 37 with a lower refractive index compared with the peripheral part 32 of the core, thereby obtaining the configuration form of the distribution of the refractive index for the three-layer structure of the convex type, containing the shell 37.

However, the proposed activities singlemode and loss curves are supported up to 100 dB/m or below, it is very difficult to realize simultaneously a sufficient increase Andeffand the reduction of dispersion slope.

For example, when considering the optical fiber type core dual form, which is used for smaller diameter, disclosed in Japanese laid patent application H8-220362/1996, the minimum slope of the dispersion is about to 0.10 PS/km/nm2in the result, this optical fiber sometimes does not meet the requirements of practical use in systems where it is strictly required to reduce the dispersion slope.

Using an optical fiber with a segmented type core, where solutions are used for larger diameter, disclosed in Japanese laid patent application H11-119045/1999 obtained characteristics close to those required in more modern systems multiplexed transmission separation by wavelength. However, since the shape of the distribution of refractive index contains a five-layer structure in which increases and decreases the refractive index, the characteristics vary essentially depending on the position, width, shape and so on for each layer. Accordingly, the manufacturing process requires high uromania each layer. Therefore, there is a limit to which you can improve the performance of manufactured products.

In addition, increasing the number of channels (i.e. the number of multiplexed wavelengths) required optical fiber with an offset dispersion, which can be used throughout a wide wavelength range transmission from 1490 to 1625 nm, which added the so-called L band (1570-1610 nm).

Known optical fiber with dispersion shifted and enlarged Andeffintended for transmission in the range of 1550 nm, so currently there is no optical fiber, which would have characteristics in the range of L, corresponding to modern requirements. In many cases, losses on the curves become large, especially in the l-band.

The present invention, which is offered subject to the conditions, described above, is to provide an optical fiber with dispersion shifted, which could satisfactorily implement the increase Andeffand the reduction of dispersion slope at the same time under such conditions, under which is implemented essentially single-mode propagation, and loss curves are supported at the level of 100 dB/is th, that would have stable characteristics and, if possible, simple structure, which, however, could make effective way.

Another objective is to provide an optical fiber with dispersion shifted, with which it is possible to satisfactorily implement the increase Andeffand the reduction of dispersion slope at the same time under such conditions, when implemented essentially single-mode propagation, and loss curves are supported at the level of 100 dB/m or less, even in a wide range of wavelengths, which added the L band overlapping wavelength from 1490 to 1625 nm.

Another task is to perform optical fiber dispersion-shifted, which has low losses at bends, especially in the l-band.

In order to solve the above problem, the first optical fiber with an offset dispersion according to the present invention is an optical fiber with dispersion shifted, which has the shape of a distribution of refractive index, containing the Central part of the core with high refractive index, a stepped part of the core with a lower refractive index n is e low refractive index compared to the stepped part of the core, which is made around the outer periphery of the stepped portion of the core, in which the optical fiber with an offset variance is used in the wavelength range selected from 1490 to 1625 nm, Andefffrom 45 to 90 μm2the dispersion slope of 0.05 to 0.14 PS/km/nm2losses at bends 100 dB/m or less and a value of chromatic dispersion from 0.5 to -8,0 PS/km/nm or from +0.05 to +10,0 PS/km/nm, and has a wavelength cutoff at which essentially is a single-mode distribution.

The second optical fiber with an offset dispersion is characterized by the fact that in the first optical fiber with an offset dispersion solution for larger diameter is the diameter of the core, and an optical fiber with an offset variance is used in the wavelength range selected from 1490 to 1625 nm, Andefffrom 45 to 70 μm2the dispersion slope of 0.05 to 0.08 PS/km/nm2losses at bends 100 dB/m or less and a value of chromatic dispersion from 0.5 to -8,0 PS/km/nm, and has an upper critical wavelength, which is essentially a single-mode distribution.

The third optical fiber with an offset dispersion is characterized by the fact that the second optical fiber with an indented display the relative difference between the refractive indices of the Central part of the core, when the refractive index of the farthest from the center of the shell is selected as a reference - as1 and the relative difference between the refractive indices of the stepped part of the core - as2, r2/r1 takes values from 4 to 12,2/1 - from 0.05 to 0.15 and1 - from 0.55 to 0.85%.

The fourth optical fiber with an offset dispersion is characterized by the fact that in an optical fiber with dispersion shifted the shell includes a first shell made around the outer periphery of the aforementioned stepped portion of the core, and a second shell having a higher refractive index compared with the first shell made around the outer periphery of the first shell.

The fifth optical fiber with an offset dispersion is characterized by the fact that in the fourth optical fiber with dispersion shifted, when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the radius of the first shell as r3, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the farthest from the center of the shell is selected as pornog the ti core - 2 and the relative difference between the refractive indices of the first shell - like3, r2/r1 takes values from 4 to 12,2/1 - from 0.05 to 0.15,1 - from 0.55 to 0.85%,3 - from 0.3 to 0% and (r3-r2)/r1 from 0.2 to 4.0.

The sixth optical fiber with an offset dispersion is characterized by the fact that in the first optical fiber with an offset dispersion solution for larger diameter is the diameter of the core, and an optical fiber with an offset variance is used in the wavelength range selected from 1490 to 1625 nm, Andefffrom 45 to 70 μm2the dispersion slope of 0.05 to 0.075 PS/km/nm2losses at bends 100 dB/m or less and a value of the chromatic dispersion of +0.05 to +10,0 PS/km/nm, and has a wavelength cutoff, which is implemented essentially single-mode distribution.

The seventh optical fiber with an offset dispersion is characterized by the fact that in the sixth optical fiber with dispersion shifted, when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part �://img.russianpatents.com/chr/916.gif">1 and the relative difference between the refractive indices of the stepped part of the core - as2, r2/r1 takes values from 4 to 12,1 - from 0.55 to 0.75% and2/1 - from 0.05 to 0.15.

The eighth optical fiber with an offset dispersion is characterized by the fact that in the sixth optical fiber dispersion-shifted shell includes a first shell made around the periphery of the stepped portion of the core, and a second shell made around its outer periphery.

The ninth optical fiber with an offset dispersion is characterized by the fact that in the eighth optical fiber with dispersion shifted, when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the radius of the first shell as r3, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the second shell is selected as a reference - as1, the relative difference between the refractive indices of the stepped part of the core - as2, the relative difference between the refractive indices of the first shell - like3, //img.russianpatents.com/chr/916.gif">1 - from 0.05 to 0.15,3 - from -0,1 0% and (r3-r2)/r1 from 0.2 to 4.0.

The tenth optical fiber with an offset dispersion is characterized by the fact that in the first optical fiber with an offset dispersion solution for smaller diameter is the diameter of the core, and an optical fiber with an offset variance is used in the wavelength range selected from 1490 to 1625 nm, Andefffrom 65 to 95 μm2the slope of the dispersion from 0.08 to 0.14 PS/km/nm2losses at bends 100 dB/m or less and the absolute value of the chromatic dispersion of 0.5 to 0.8 PS/km/nm, and has a wavelength cutoff, which is implemented essentially single-mode distribution.

11th optical fiber with an offset dispersion is characterized by the fact that in the tenth optical fiber with dispersion shifted, when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the shell is selected as a reference - as1, the relative difference between the refractive indices of the stepped part of the core - as2, the ratio r2/r1 - x is, ,08y0.22 and 0.6% of11,2%.

12-th optical fiber with an offset variance is a tenth of an optical fiber with an offset dispersion having a wavelength of zero dispersion in the direction of longer wavelengths in comparison with the used wavelength range.

13th optical fiber with an offset dispersion is characterized by the fact that in the 12th optical fiber with dispersion shifted, when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the shell is selected as a reference - as1, the relative difference between the refractive indices of the stepped part of the refractive index as2, r2/r1 - x and2/1 - as, 6x7, with 0.1yof 0.18, y(-0,02 x+0,24), 0,6%11.2%, Andif second optical fiber with an offset dispersion is characterized by in the 12th optical fiber dispersion-shifted 7x8, with 0.1yof 0.16, y(-0,016 x+0,21), 0,6%11.2%, Andeffaccepts values from 70 to 80 μm2and the slope of the dispersion is 0,130 PS/km/nm2or less.

15th optical fiber with an offset dispersion is characterized by the fact that in the 12th optical fiber dispersion-shifted 7x8,5, 0,1y0,16, (-0,02 x+0,26)(-0,02 x+0,32), 0,6%11.2%, Andeffaccepts values from 75 to 85 μm2and the slope of the dispersion is is 0.135 PS/km/nm2or less.

16-th optical fiber with an offset variance is a tenth of an optical fiber with an offset dispersion with wavelength zero dispersion at the edge of the shorter wavelengths in comparison with the used wavelength range.

17-th optical fiber with an offset dispersion is characterized by the fact that r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the shell is selected as a reference - as1, the relative difference between the refractive indices of the stepped part of the core - as2, r2/r1 - x and2/1 - as, 5x8, 0,12y0,22, (-0,02 x+ 0,24)y(-0,02 x+0,34), 0,6%11.2%, Andeffaccepts values from 65 to 75 μm2and the slope of the dispersion is 0,110 PS/km/nm2or less.

18-th optical fiber with an offset dispersion is characterized by the fact that in the 16th optical fiber with dispersion shifted 5,5x8, 0,12y0,20, (-0,02 x+0,25)y(-0,02 x+0,33), 0,6%11.2%, Andeffaccepts values from 70 to 80 μm2and decl is specified topics in the 16th optical fiber dispersion-shifted 6x8, 0,12y0,20, (-0,02 x+0,26)y(-0,02 x+0,35), 0,6%11.2%, Andeffaccepts values from 75 to 85 μm2and the dispersion slope of 0.125 PS/km/nm2or less.

The invention is illustrated by reference to the accompanying drawings, in which: Fig. 1A depicts a diagram of a first example of the shape of the distribution of refractive index for optical fiber dispersion-shifted in accordance with the present invention; Fig. 1B depicts a diagram of a second example of the shape of the distribution of refractive index for optical fiber dispersion-shifted in accordance with the present invention; Fig. 2 depicts a graph which shows the analysis of example, when the first example of the shape of the distribution of refractive index, are presented in chart form in Fig.1A, is used in the first embodiment; Fig.3 depicts a graph which shows an example of the dependence of the values of the chromatic dispersion as a function of wavelength for the optical the Oia losses at bends in accordance with the combinations of values of3 and (r3-r2)/r1 when the second example of the shape of the distribution of the refractive index shown in chart form in Fig.1B, is used in the first embodiment; Fig. 5 depicts a graph which shows the analysis of example, when the shape of the distribution of the refractive index, are presented in chart form in Fig.1A, is used in the second embodiment; Fig. 6A and 6B depict graphs of losses at bends Andeffaccordingly, according to the combinations of values of3 and (r3-r2)/r1 when the second example of the shape of the distribution of the refractive index shown in chart form in Fig.1B, is used in the second embodiment; Fig. 7 depicts a graph of the results of the analysis, representing the traces of solutions to a smaller diameter when the values of the2/1 and1 change if the values for r2/r1 5, 7 and 9, respectively, in the third embodiment; Fig. 8 depicts a graph showing the distribution of the characteristic values associated with changes in2/1 and1, when r2/r1 = 7 in the third embodiment;
Fig. 9 depicts a graph of the distribution1 and1, when r2/r1 = 9 in the third embodiment;
Fig.10A depicts a diagram of an example of a form of distribution of the refractive index for optical fiber dispersion-shifted prior art;
Fig.10B depicts a diagram of an example of a form of distribution of the refractive index for optical fiber dispersion-shifted prior art;
Fig.10C depicts a diagram of an example of a form of distribution of the refractive index for optical fiber dispersion-shifted prior art.

The PREFERRED IMPLEMENTATION of the PRESENT INVENTION
Optical fiber with dispersion shifted, according to the present invention, has the shape of a distribution of refractive index, containing the Central part of the core with high refractive index, a stepped part of the core with a lower refractive index compared with the Central part of the core, made around the outer periphery of the Central part of the core, and a shell with a lower refractive index compared to the stepped part of the core, made around the outer periphery of the stepped part of serdtseva, where in the used wavelength range selected from a range of 1490-1625 nm Andeffaccepts values from 45 to 90 μm2the slope of the dispersion from 0.05 to 0.14 PS/km/nm2losses at bends 100 dB/m or less and a value of chromatic dispersion from 0.5 to -8,0 PS/km/nm or from 0.05 to 10 PS/km/nm, which has a wavelength cutoff, which is implemented essentially single-mode distribution.

Below is a detailed description of the present invention on the example of the first, second and third embodiments.

The FIRST VERSION of the IMPLEMENTATION
In Fig.1A presents the first example of the shape of the distribution of refractive index for optical fiber dispersion-shifted in the first embodiment.

This form of distribution of the refractive index has the configuration of the core 4, in which a stepped portion 2 of the core is made around the outer periphery of the Central part 1 of the core and the shell 7 of the single-layer structure that has a constant refractive index, performed around the outer periphery of the core 4.

The Central part 1 of the core has the highest refractive index, a stepped portion 2 of the core has a refractive index lower than that of C is guilty.

The symbols r1 and r2 in the figure denote respectively the radii of the Central part 1 of the core and a stepped portion 2 of the core, whereas1 and2 denote, respectively, the relative difference between the refractive indices of the Central part 1 of the core and the relative difference between the refractive indices of the stepped portion 2 of the core, when the refractive index of the shell 7 is used as a reference.

In this example, the Central portion 1 of the core and a stepped portion 2 of the core is made of quartz glass doped with germanium, which was added germanium, showing the effect of increasing the refractive index, whereas the shell 7 is made of pure quartz glass.

In addition, the shape of the distribution of the refractive index of the optical fiber with dispersion shifted the boundary between each layer (i.e. the Central part 1 of the core, a stepped part 2 of the core and the shell 7) will not necessarily be specific, as shown in Fig.1A, but may instead be rounded, which is manifested in the so-called SAG, and will not, in particular, limited up until now will be the exercise.

In an optical fiber with dispersion shifted this case for a wavelength range extending from 1490 to 1625 nm, and typically from 1490 to 1610 nm, is used, the main wavelength range and a wavelength range having a suitable width for wavelengths selected from these ranges when defining the technical conditions of option exercise. These wavelength ranges is basically divided into three wavelength range in accordance with a gain range of wavelengths, which have fiber-optical amplifiers used in optical communication system. More specifically, the conventional designation for a wavelength range extending from 1490 to 1530 nm is the range of S, for a range of wavelengths extending from 1530 to 1565 nm - range and for a range of wavelengths extending from 1565 to 1625, but usually from 1490 to 1610 nm, the range of L. In modern systems mainly used range From, but are currently being developed systems are expected to be used in addition to the range With the range of L to satisfy the requirements of the ranges, showing an increased amount of gear.

Andefffound by the following formula:

where the e implementation when Aeffin the used wavelength range of less than 45 μm2non-linear optical effect is suppressed enough. It is very difficult to manufacture an optical fiber with an offset dispersion in which Aeffexceeds 70 μm2.

As mentioned above, the smaller the value of dispersion slope in the wavelength range, the better. In this embodiment, it is possible to realize very small values for the dispersion slope in the wavelength range, i.e. from 0.05 to 0.08 PS/km/nm2. When exceeding the value of 0.08 PS/km/nm2the dependence of the wavelength on the value of the chromatic dispersion becomes very large, which is sometimes certain difficulties for the implementation of this option when used in the systems division multiplexing wavelengths. At values less than 0.05 PS/km/nm2it becomes very difficult to process.

Under losses at bends refers to the value that is observed in the wavelength range under the condition that the curve diameter (2R) is equal to 20 mm

The smaller loss in bends, the better. In this embodiment, the losses for bends up to 100 dB/m or less, and preferably 40 dB/the verge transmitted optical fiber with dispersion shifted, and during operations gaskets, or other works there is excessive loss, which is also a disadvantage.

In this embodiment, the value of the chromatic dispersion are within a range from 0.5 to -8,0 PS/km/nm. When this value becomes more and 0.5 PS/km/nm, the value of the chromatic dispersion reaches zero, and at once there is four-wave mixing, which is one of nonlinear optical effects, which is a disadvantage. When the value is less than -8,0 PS/km/nm is the distortion of the waveform due to the induced dispersion and distortion characteristics of the transmission becomes very large, which creates additional problems. However, the range of valid values variance in practice will vary depending on the distance at which the transfer takes place, and other structural factors of the system.

In addition, because the optical fiber with dispersion shifted in this embodiment, is a single-mode optical fiber, it is necessary to have a wavelength cutoff, which essentially would ensure single-mode propagation in the used wavelength range.

Typically, the wavelength cutoff is determined using values based on SP is evident and Telegraph communication (the modern name ITU-T)"). However, in real conditions of use of the optical fiber with a large length of single-mode propagation is possible even in the case where this value is located on the edge of the longer wavelengths relative to the lower limit value in the used wavelength range.

Therefore, in the optical fiber dispersion-shifted version of the implementation wavelength cutoff, which is determined using the method of 2m, is installed with the possibility of single-mode propagation in accordance with the length of the optical fiber with dispersion shifted and used range of wavelengths. More specifically, if the wavelength cutoff in the way that 2m is 1800 nm or less, provided that the length is equal to approximately 5000 m or more, it is possible to influence single-mode propagation in the used wavelength range as described above.

Configuration satisfying such characteristics described below together with its historical researches.

In this embodiment, first is used for larger diameter as the diameter of the core, as described previously. More specifically, when installing the structural parameters that satisfy the numerical range is the same using simulation, installation is made so that the core diameter was the solution for a larger diameter, and are set such settlement conditions which satisfy such characteristic values as aeffthe slope of the dispersion, and so forth, in the wavelength range required for use, as described above. In addition, based on the actual method of manufacturing optical fiber with dispersion shifted according to this variant implementation, you can use a known method, such as HOP (chemical vapor deposition, CVD), COPTS (chemical vapor deposition on an end face of the workpiece, VAD) and so on.

In Fig. 2 depicts a graph which shows an example of analysis in the case when the shape of the distribution of the refractive index for this first example.

Values 5, 7 and 10, corresponding to the symbolsand +, which are shown in the graph are the values for r2/r1 (ratio of speed increase), which represents the ratio of the radii of the Central part 1 of the core and a stepped portion 2 of the core (Fig.1A). The graph is Aeffpending on the horizontal axis, and the slope of the dispersion pending on the vertical is the increase in the value of r2/r1, while the slope of the dispersion tends to decrease. In order to fulfil the requirements of ranges of numerical values for the value of the chromatic dispersion and losses in the bends, as mentioned previously, it is preferable that r2/r1 is 4 or more. When the ratio is less than 4 it is very difficult to implement features that will be better than in the known optical fiber dispersion-shifted. When the value is exceeded, the relationship 12 output falls, which is problematic.

It is also necessary that values relationships2/1 was within the range of 0.05 to 0.15. If the value is less than 0.05 loss on the curves become large, which is a disadvantage. When exceeding the value of 0.15 wavelength cutoff becomes long, and then, in some cases, it is impossible to maintain a stable single-mode transmission.

1 is selected in the range of 0.55 to 0.85 per cent. When this value becomes less than 0.55%, very difficult to determine the useful range of wavelengths in the range of-0.5 - -8,0 PS/km/nm. When1 becomes large, the variance value can be made small, but when exceeding 0,85% AndeffNY the numerical values of these numerical ranges for r2/r12/1 and1 in order to obtain the characteristics of the optical fiber with dispersion shifted according to this variant implementation.

In addition, in an optical fiber with dispersion shifted, according to the present variant implementation, in particular, r2, i.e. the radius of the core, is not limited. Typically this value will be in the range of 10-25 microns. The external diameter of the shell 7 is usually chosen equal to approximately 125 microns.

Table 1 shows these specific examples of the calculation of optical fibers, dispersion-shifted, which satisfy such conditions. In this table,cf- wavelength cutoff of the fiber, which is obtained on the basis of the method 2m,opthe wavelength at which the measured characteristics, and DMP - diameter mode field.

In each of these examples, the characteristics that satisfy the preferable numerical ranges for aefftilt variance, the values of the chromatic dispersion, losses at bends and wavelength cutoff, which is suitable for multiplexed transmission separation by wavelength.

Graph (a) shown in Fig.3, the e l e C shown in table 1. All profiles are shown in the table.1 have approximately the same dependence of the wavelength values of dispersion and 0.5 PS/km/nm or less in the range called range, up to approximately 1570 nm, the result shows that these optical fibers suitable for transmission systems with MRD (division multiplexing in wavelength), which uses a range From.

Upon receipt of the dependency of the wavelength from the value of the chromatic dispersion, as shown in the graph (b) in Fig.3, the range in which you can get the values of the chromatic dispersion and 0.5 PS/km/nm or less, can be increased to approximately 1600 nm. That is, compared with the optical fibers, which have the characteristics shown in the graph (a) in Fig.3, the optical fiber having the characteristic shown in graph (b) in Fig. 3, allow to increase the range of wavelengths that can be used in the transmission system MRDV. Table 2 presents examples of the types of profile, which lead to the characteristics shown in graph (b) in Fig.3.

In Fig.1B depicts a second example of the shape of the distribution of refractive index for optical fiber dispersion-shifted hundred forms of distribution of refractive index in the first example, as described previously, the fact that the shell 7 has a two-layer structure containing a first membrane 5 and the second sheath 6.

In this shell 7, the refractive index of the farthest from the center of the second sheath 6 is high, whereas the first sheath 5 has a lower refractive index than that of the second sheath 6.

In this figure, the symbol r3 is the radius of the first shell 5, whereas3 - the relative difference between the refractive indices of the first casing 5, when the refractive index of the farthest from the center of the second sheath 6 is selected as a reference. The symbols r1 and r2 represent the same as in Fig.1A, whereas1 and2 represent, respectively, the relative refractive index difference between the Central part 1 of the core and a stepped portion 2 of the core, when the refractive index of the second sheath 6 is selected as a reference.

In this example, the Central portion 1 of the core and a stepped portion 2 of the core is made of quartz glass doped with germanium, the first sheath 5 is made of quartz
glass doped with fluorine, which was added fluoride, showing the effect of reducing the index of prelimininary each layer (i.e. the Central part 1 of the core, speed part 2 of the core, the first shell 5 and the second sheath 6) will not necessarily be defined, but instead may be rounded, which is manifested in the so-called sagging.

In an optical fiber with dispersion shifted, which has the same shape of the distribution of refractive index, as in the second example, by setting the corresponding structural parameters for the Central part 1 of the core and a stepped portion 2 of the core, that is, r1 and1, on the one hand, and r2 and2, on the other hand, in such a way that they were satisfactory in numerical ranges for r2/r12/1 and1, shown in the first example described previously, so that in this embodiment can be realized Andeffand other characteristic values, obtained the same advantages as in the first example.

When making configuration is added to the first sheath 5, it becomes possible additional reduction of losses at bends in comparison with the first example. In the absence of specific limitations and choosing repre dB/m or less, and preferably at the level of 40 dB/m or less.

Moreover, an advantage which you realize is that depending on how the structural parameters (and their combinations) are installed, it is possible to make the wavelength cut even shorter, or you can further increase Andeff.

In Fig.4 depicts a graph showing the changes of the losses at bends, the resulting combinations3 and (r3-r2)/r1 when3 and r3 is changed while maintaining a constant1,2, r1 and r2. Values (r3-r2)/r1 pending on the horizontal axis, and the values of3 pending on the vertical axis. When this1=0,61%,2=0.05% and r2/r1=10.

From this graph it is seen that the loss curves become smaller with increasing shifts3 from 0 to negative values, i.e. the larger the shift, the less is the refractive index of the first sheath 5, and the reduction of the refractive index, which is caused first by the shell 5, is becoming more. Loss curves also tend to decrease with increasing values of (r3-r2)/r1, that is, increasing the value of r3.

Thus, as losses on izgib freedom of installation of the structural parameters (3, r3) for the first shell 5 in order to satisfactorily implement suitable numerical range for the losses in the bends.

In Fig. 4, for example, losses in the bends of 30 dB/m or approximately the same can be obtained by using a combination where (r3-r2)/r1=0.6 and3=-0,18%, and using a combination where (r3-r2)/r1=1.8 and3=-0,05%. Accordingly, if we consider only losses at bends, it is possible to take each of these combinations.

However, since transmission losses tend to increase when the value of3 becomes small (that is, when this value leads to a shift in the negative direction), preferably3 was equal to 0.3 per cent or more.

In addition, as in the manufacture of problems arise when the value of (r3-r2)/r1 becomes large (that is, when r3 becomes large), preferably, (r3-r2)/r1 is 4.0 or less. And as3 must be set to a small value when (r3-r2)/r1 is small, the transmission loss tends to increase, and problems arise in the manufacture, resulting in preferably (r3-he shifted dispersion, which satisfy the conditions listed below. In each of these examples, the characteristics that satisfy the preferable numerical ranges for aefftilt the dispersion values of the chromatic dispersion, losses at bends and wavelength cutoff in this embodiment, which are analogous system for multiplexed transmission separation by wavelength. The calculation examples shown in this table represent examples of applications, mainly in the range of C. As in the first example, it is possible calculations that satisfy the technical conditions for the L band, and not just for the range From.

In this embodiment, the obtained optical fiber dispersion-shifted, which satisfies the conditions of essentially single-mode propagation and shows losses at bends 100 dB/m or less, whereby it is possible also to adequately increase Andeffand to sufficiently reduce the slope of the dispersion. More specifically, with this option, the implementation you can implement very small values for slope variance.

Thus, it is possible to perform optical fiber dispersion-shifted, which is practically an ID which is relatively simple form of the distribution of refractive index, there are several structural parameters that need to be controlled in the manufacturing process, which is an advantage in the manufacture and makes it possible to effectively obtain the required characteristics.

The SECOND VARIANT IMPLEMENTATION
The first example of the shape of the distribution of refractive index in an optical fiber with an offset variance of this second variant implementation is the same as the shape of the distribution of the refractive index shown in Fig. 1A, previously described, while the view from the dual form is done through the core 4, in which a stepped portion 2 of the core is made around the outer periphery of the Central part 1 of the core and the shell 7 of the single-layer structure having a uniform refractive index, made around its outer periphery.

The Central part 1 of the core has the highest refractive index, manual part 2-core has a lower refractive index compared with the Central part 1 of the core and the shell 7 has a refractive index lower than that of the stepped portion 2 of the core.

In this example, the Central portion 1 of the core and a stepped portion 2 of the core is made of quartz CTE is I of refraction, while the shell 7 is formed, for example, of fine silica glass.

In addition, the shape of the distribution of the refractive index of the optical fiber with dispersion shifted the boundaries between each layer (i.e. the Central part 1 of the core, a stepped part 2 of the core and the shell 7) will not necessarily be defined, but instead may be rounded, which is manifested in the so-called slack, and in this case there is no specific limitation as long until you would be able to implement effective way characteristics of the optical fiber with dispersion shifted, according to the present variant implementation.

The second example of the shape of the distribution of refractive index in an optical fiber with dispersion shifted this option is the same as the example shown in Fig.1B and described above.

This form of distribution of refractive index is different from the shape of the distribution of the refractive index of the first example of the fact that the shell 7 in this case has a two-layer structure containing a first membrane 5, which is made around the outer periphery of the stepped portion 2 core (core 4), and the second is made of quartz glass, doped with fluorine, which was added fluoride, which helps to reduce the refractive index.

The wavelength range used in optical fiber with dispersion shifted this variant implementation is selected from the range 1490-1625 nm, but is usually in the range 1490-1610 nm, a wavelength range with a suitable width of the wavelength. For example, the wavelength range (such as 1500-1520 nm) is selected from the range 1490-1530 nm, which has a given width of the wavelength. Select a range of wavelengths (such as 1540-1565 nm) from a range of 1530-1570 nm, which has a given width of the wavelength. Select a range of wavelengths (such as 1570-1600 nm), which has a given width of the wavelength range of 1570-1625 nm, which is the so-called L band, typically in the range 1570-1610 nm.

Thus, one of the characteristics of this alternative implementation is that the used wavelength range can be selected from l-band.

On the other hand, the entire range 1490-1625 nm can be used to make a range of wavelengths (wavelength range transmission).

In an optical fiber with dispersion shifted, according to the present variant implementation, the value of the chromatic dispersion reaches zero, and quickly occurs four-wave mixing, which is one of nonlinear optical effects, which is a disadvantage. On the other hand, when exceeding the values +10,0 PS/km/nm is the distortion of the waveform and sometimes markedly deteriorating transmission characteristics.

Value Andeffare using the same mathematical formula that was given in the first embodiment described earlier.

Optical fiber with dispersion shifted in this embodiment, has Aefffrom 45 to 70 μm2in the used wavelength range, resulting in possible to suppress nonlinear optical effects. When Aeffless than 45 μm2the reduction of nonlinear optical effects becomes insufficient, whereas when it exceeds 70 μm2to become a very difficult manufacturing process.

Very small values from 0.050 to 0.075 PS/km/nm2you can implement for slope variance in the used wavelength range. In the result, it is possible to prevent the deterioration of the transmission caused by the inclination of the variance in the multiplexed transmission separation by wavelength.

Loss curves are determined in the same way that my set at the level of 100 dB/m or less, and preferably at the level of 50 dB/m or less. When exceeding the value of 100 dB/m transmission losses increase rapidly due to weak curves, which is subjected to optical fiber dispersion-shifted, and there are excessive losses during the operation of the strip or other works, which is a disadvantage.

In addition, as in this embodiment, the optical fiber with an offset variance is a single-mode optical fiber, it is necessary to have a wavelength cutoff, which guarantees essentially single-mode propagation in the used wavelength range.

As previously established, conventional wavelength cutoff is determined using the values based on the way 2m CCITT (which is hereinafter referred to as way 2m). However, in real conditions of use of the optical fibers of great length, single-mode propagation is possible even in the case where this value is located on the edge of the longer wavelengths relative to the lower limit value in the used wavelength range.

Therefore, in an optical fiber with dispersion shifted, according to the present variant implementation, the wavelength cutoff determined by using method 2m, is set so that a single-mode distribution was in the a range of wavelengths. More specifically, if the wavelength of the cutoff obtained by way of 2m, is 1800 nm at large length of 5000 m or approximately the same, it is possible to realize single-mode propagation in the used wavelength range, as described above.

In addition, in this embodiment, the solution for a larger diameter is used for the core diameter (r22). In particular, as will be described below when installing the four structural parameters: r2, r12 and1 for the form of the distribution of the refractive index shown in Fig.1A, and when you install the six structural parameters, which include the above plus r3 and3 to form the distribution of the refractive index shown in Fig.1B, settlement conditions established so that the core diameter was the solution for a larger diameter, so that such characteristic values as aeffand the slope of the dispersion, satisfy the desired wavelength range described above. In addition, you can use these known methods, SVD and VAD as a real method of manufacturing optical fiber mixed with the dispersion according to Alekna offset dispersion in this embodiment has a three-layer or four-layer configuration, and as this is a relatively simple step form, it is relatively easy to manage structural parameters.

In Fig. 5 shows a graph depicting an example of the results of the analysis of the structural materials of the optical fiber dispersion-shifted, which has the shape of a distribution of the refractive index shown in Fig.1A.

Values 5, 7 and 10, corresponding to the symbolspresented on the chart, are the values for r2/r1, which is the ratio of the radii of the Central part 1 of the core and a stepped portion 2 of the core (Fig. 1A). Value Andeffpending on the horizontal axis, and the slope of the dispersion pending on the vertical axis, each of which is the value for a wavelength of 1550 nm.

From this graph it is seen that the greater the value of r2/r1, the more you can reduce the slope of the dispersion. In order to obtain values of losses at bends and aeffwithin the preferred numerical ranges mentioned above, r2/r1 should be set at 4 or above. When this value is less than 4, it is very difficult to obtain good characteristics. On the other hand, when the set value exceeds 12, output falls. Consequently, the real upper limit is selected raw.

In addition, in this embodiment,1 is set in the range from 0.55% to 0.75% in the form of the distribution of the refractive index shown in Fig. 1A and 1B. When1 less than 0.55%, it is very difficult to establish the value of the chromatic dispersion in the desired range, and the loss on the curves tend to a large increase. If1 greater than 0,75%, Andeffit is very difficult to make large enough.

It is preferable that the relation2/1 ranged from 0.05 to 0.15. At values below 0.05 loss on the curves become large, which is a disadvantage. When the value is exceeded 0.15 slope variance will exceed a certain range, which is problematic for use in multiplexed transmission separation by wavelength. Table 4 presents the simulation results, showing the structural parameters and characteristic values for specific examples of the calculation of optical fibers, dispersion-shifted, which have the shape of the distribution of the refractive index (Fig.1A) satisfying these conditions.

In each example, preferred is Persia, the values of the chromatic dispersion, losses at bends and upper critical wavelength, and the resulting characteristics that are suitable for multiplexed transmission separation by wavelength.

Furthermore, these characteristic values are obtained even when the appropriate values are selected and combined from the numerical ranges of structural parameters, which are described above, it is necessary to choose a combination of structural parameters that satisfy the characteristic values from the graph(s) and simulation results described above. Therefore, as it is very difficult to determine optical fiber dispersion-shifted version of the implementation using the structural parameters, the technical terms are given here using the characteristic values.

In addition, the shape of the distribution of the refractive index (Fig.1B) establish3 and r3. Choosing the shell 7 with a two-layer structure containing a first membrane 5 and the second sheath 6, the wavelength cutoff can be done even shorter than in the first embodiment, by combining (installation) of the structural parameters and can additionally took the ax and the relationship between3 and aeffaccordingly, in the shape of the distribution of refractive index, which contains a two-layer structure of the shell shown in Fig.1B. The calculated wavelength is 1550 nm.

All values1,2, r1 and r2 are common and are set at a constant value. 1=0,56% and2=0,06%.

From these graphs it is seen that the value of Aeffcan be more, when3 becomes smaller, but the losses at bends also be more.

The nature of the change will also vary depending on the values of the ratio (r3-r2)/r1.

In accordance with these structural parameters are set so as to meet the requirements of a preferable numerical ranges of the characteristics described earlier, taking into account correlations between the structural parameters and characteristics.

It is preferable to choose the value of3, is equal to minus 0.1 per cent or more. The reason in this case is that when3 less -0,1%, the transmission characteristics are sometimes worse depending on combinations of other structural parameters.

Preferably, However, when (r3-r2)/r1 is small, and3 should be small. Therefore, in order to limit the deterioration of the transmission characteristics, as described previously, (r3-r2)/r1 should be 0.2 or more.

Table 5 shows the simulation results showing the structural parameters and the characteristic values in the examples of specific calculations of optical fibers with dispersion shifted that satisfy these conditions.

In each example, the preferred numerical ranges are implemented for aefftilt variance, the values of the chromatic dispersion, losses at bends and wavelength cutoff in the optical fiber dispersion-shifted version of the implementation, and the resulting characteristics that are suitable for multiplexed transmission separation by wavelength.

The calculated wavelength for optical fiber dispersion-shifted, are shown in tables 4 and 5, is 1550 nm.

The results of the same simulation, which was conducted with a design wavelength that is installed on the value of 1610 nm, are shown in tables 6 and 7. Characteristic values that satisfy the numerical ranges in this embodiment, received th, which are presented in tables 4-7, not only in the range of 1550 nm, but also in a wider range (for example, 1490-1610 nm), which added wavelengths 1570-1625 nm, it is possible to make small chromatic dispersion and losses at bends and to guarantee single-mode transmission, while at the same time due to the increase Andeffyou can suppress nonlinear optical effects and due to the small slope of the dispersion can limit the deterioration of the transmission when the multiplexed transmission separation by wavelength. In accordance with this improvement of the transmission characteristics can be implemented even in the multiplexed transmission separation by wavelength, which is used in a wide range of wavelengths, which added the l-band.

The advantages realized in an optical fiber with dispersion shifted this variant implementation.

For example, under conditions of essentially single-mode propagation and maintain losses at bends at the level of 100 dB/m or less simultaneously and satisfactorily implement the suppression of nonlinear optical effects due to the increase Andeffand the reduction of dispersion slope and you can get a good characteristies by wavelength.

In addition, because of the relatively simple step patterns, you can easily manage the structural parameters in the manufacturing process and it is possible to efficiently manufacture an optical fiber with dispersion shifted, which has stable characteristics.

In addition, the characteristics mentioned above can be maintained even in a wide wavelength range, which stretches from 1490 to 1625 nm with the added range L, and it is possible to increase the coverage of telecommunication and higher transmission volumes using systems division multiplexing wavelengths.

Valid real losses at bends can be implemented, in particular, in the l-band.

A THIRD OPTION EXERCISE
One example of the shape of the distribution of refractive index in an optical fiber with dispersion shifted in this embodiment is the same as in Fig.1A, previously described, in accordance with which the optical fiber with dispersion shifted contains the core 4 having a stepped portion 2 of the core, which is made around the outer periphery of the Central part 1 of the core, and a shell 7 with a single-layer structure having a uniform refractive index, which is run, manual part 2-core has a lower refractive index compared with the Central part 1 of the core and the shell 7 has a low refractive index compared to the stepped part 2 the core.

In this example, the Central portion 1 of the core and a stepped portion 2 of the core is made of quartz glass doped with germanium, which was added germanium, which shows the effect of increasing the refractive index, whereas the shell 7 is formed of pure quartz glass.

In addition, the shape of the distribution of the refractive index of the optical fiber with dispersion shifted the boundary between each layer (i.e. the Central part 1 of the core, a stepped part 2 of the core and the shell 7) may not be certain, but may instead be rounded, which is manifested in the so-called slack, and not necessarily, in particular, will be limited up until now will be apparent characteristics of the optical fiber with dispersion shifted, according to the present variant implementation.

For the used range of wavelengths in an optical fiber with dispersion shifted, according to the present variant is, depending wavelength range gain in which operates a fiber-optic amplifier, which is used, for example, in an optical communication system, the wavelength range (for example, 1500-1520 nm), which has a given width of a wavelength selected from the range 1490-1530 nm. Or selected range of wavelengths (such as 1540-1565), which has a given width of the wavelength range of 1530-1570 nm. Or selected range of wavelengths (such as 1570-1600 nm), which has a given width of the wavelength range of 1570-1625 nm, from which it follows that the range of 1530-1570 nm is currently the most used.

Value Andefffound using the same formula that was given in the first embodiment.

In this embodiment, since Aeffchanges in the range of from 65 to 95 μm2in the used wavelength range, it is possible to suppress non-linear optical effects. When the value is exceeded 95 μm2the manufacturing process becomes very difficult.

The dispersion slope in the wavelength range is from 0.08 to 0.14 PS/km/nm2. If multiplexed transmission separation by wavelength it is within this range, it is possible to prevent a significant wow is it ever.

The smaller loss in bends, the better. In this embodiment, the losses for bends up to 100 dB/m or less, and preferably 50 dB/m or less. When exceeding the value of 100 dB/m fast increase of transmission loss due to weak curves, which is subjected to optical fiber dispersion-shifted, and there are bad losses during the operation of the strip or other works, which is a disadvantage.

The absolute values of the chromatic dispersion is in the range from 0.5 to 8.0 PS/km/nm. When the absolute value is less than 0.5 PS/km/nm, the value of the chromatic dispersion reaches zero, which is a disadvantage, as quickly occurs four-wave mixing, which is one of nonlinear optical effect. On the other hand, when exceeding the values of 8.0 PS/km/nm is the distortion of the waveform and increasingly deteriorating transmission characteristics.

In addition, as will be described below in more specific terms, as the value of the chromatic dispersion can be controlled with positive or negative values, it is possible to take into account the different requirements for optical communication system, and can perform optical is because the optical fiber with dispersion shifted in this embodiment, is a single-mode optical fiber, you must have a wavelength cutoff, which guarantees essentially single-mode propagation in the used wavelength range.

Conventional wavelength cutoff is determined by using values based on the way 2m CCITT (which is hereinafter referred to as way 2m). However, in real conditions of use of the optical fibers of great length, single-mode propagation is possible even in the case when this value is over the far edge of the wavelengths relatively lower limit value in the used wavelength range.

Therefore, in an optical fiber with dispersion shifted, according to the present variant implementation, the wavelength cutoff, which is determined using the method of 2m, is set so that it is possible singlemode propagation in accordance with the length of the optical fiber with dispersion shifted and used range of wavelengths. In particular, if the wavelength cutoff in the way that 2m is 1800 nm under conditions of great length is approximately 5000 m or more, it is possible to realize single-mode propagation in the used wavelength range, as described above.

Moreover, in this embodiment, the solution for meeh structural parameters: r2, rl,2 and1, the estimated parameters are set so that the core diameter was the solution for a smaller diameter, so that such characteristic values as aeffand the slope of the dispersion, satisfy the desired wavelength range, as described above. In addition, it is possible to use known methods, such as HOP and COPTS, as a real method of manufacturing optical fiber with dispersion shifted, according to the present variant implementation.

In Fig. 7 depicts a graph which shows the results of the analysis of the structural parameters of the optical fiber with dispersion shifted and shows traces of solutions for smaller diameter when changing2/1 and1, when the value of r2/r1 is equal to 5, 7 and 9, respectively.

Curves2/1 represent characteristics change1 while maintaining relationships2/1 at constant values, which are shown on the curves. On the other hand, curves1 represent characteristics change

When r2/r1=9, for example, when moving from right to left along the curve2/1 =0,14 graphics1 is changed from 0.9 to 2.0. Then the point where, for example, curve2/1 =0,14 intersects the curve1=1,4, displays the characteristics of the optical fiber with dispersion shifted when2/1 =0.14 and1=1,4.

Moreover, the analysis conditions are such that the wavelength equal to 1550 nm and the value of the chromatic dispersion at the wavelength is -2,0 PS/km/nm. Wavelength zero dispersion though is not constant, as it is the slope of the dispersion, however, is approximately equal to 1560 nm or above on the edge of the longer wavelengths of the used wavelengths (wavelength range).

In Fig.8 and 9 are graphs similar to the graph in Fig.7, which shows the distribution of the characteristic values associated with changes2/1 and1, when r2/r1 is equal to 7 and 9 respectively. These charts also show raspredeliteli also shown on the curves, for which2/1 0.10, 0.12 and, of 0.14 and 0.16. For example, if2/1 =0.10 wavelength cutoff distributed in the range from 1.0 to 1.1. On the other hand, when2/1 =0,12 wavelength cutoff distributed in the range of 1.1-1.2 and 1.2-to 1.3. And as you can see, when the value of2/1 is constant, the wavelength cutoff becomes shorter at higher values of1.

Curves the slope of the dispersion are in the form of an inverted U, distributed in a contour picture. The farther to the edge of this distribution contour pattern, the smaller the variance, and the closer to the inner part, the bigger it is.

Accordingly, in the graph shown in Fig. 8, for example, if2/1 =0.14 and1=1,4 (point, where the curve2/1 ==0,14 intersects the curve1= 1,4) receive an optical fiber with dispersion shifted, where the wavelength cutoff is in the range of 1300-1400 nm and the dispersion slope is in the range 0,122-0,124 PS/km/nm2.eff
equal to 65 μm2or more.

On the other hand, when r2/r1 is large, you can get a higher value Andeff. However, as can be seen when comparing the graphs shown in Fig.8 and Fig.9, the slope of the dispersion tends to become large at high values of r2/r1. In order to obtain an optical fiber with an offset dispersion suitable for the systems division multiplexing wavelengths, it is preferable that the dispersion slope in the wavelength range was equal to 0.14 PS/km/nm2or less, and with this purpose, r2/r1 do is 10 or less.

Accordingly, when r2/r1=x range 5x10 meets the requirements.

In addition, while too small values of2/1 loss at bends become large, which is unsuitable for practical use, resulting in a2/1 do is 0.08 or more. On the other hand, if2/1 is too large, the wavelength cutoff becomes long and can no longer guarantee single-mode 916.gif">1 make equal to 0.22 or less.

Accordingly, when the condition is met2/1=in the range of 0.08y0,22 meets the requirements.

2/1 (y) can also be adjusted in accordance with acceptable losses at bends and desired wavelength cutoff in different individual optical communication systems.

1 is chosen in the range of 0.6 to 1.2%. When this value becomes less than 0.6% of losses on the curves become too large, and in some cases, the value of the chromatic dispersion cannot be maintained at the required value. When exceeding 1,2% cannot sufficiently increase Andeffand in some cases the Rayleigh losses become large.

The preferred ranges for these parameters, i.e. for r2/r1 (x)2/1 (y) and1, are the same as in the case where the wavelength of zero dispersion is on the edge of the longer wavelengths of the used wavelength range.

The calculation is carried out so that to the ticks of the optical fiber with dispersion shifted, under this option implementation.

In addition, in an optical fiber with dispersion shifted, according to the present variant implementation, r2, i.e. the radius of the core, is not particularly limited, but its values typically are in the range of 4-12 μm. And the external diameter of the shell 7 (i.e. optical fiber with dispersion shifted) is typically 125 microns.

Moreover, in an optical fiber with dispersion shifted, according to the present variant implementation, the limits of the structural parameters will differ depending on whether the fiber wavelength zero dispersion at the edge of the longer wavelengths or at the edge of the shorter wavelengths of the used wavelength range.

When the wavelength of zero dispersion is on the edge of the longer wavelengths of the wavelength range enters into force limit mentioned below.

In particular, in order to obtain an optical fiber with dispersion shifted with aeff=65-75 μm2and slope of dispersion 0,125 PS/km/nm2or less, must meet the conditions listed below.

When r2/r1 is expressed by x and2/1 - with y,
6(-0,02 x+0,24) and
0,6%11,2%.

And in order to obtain an optical fiber with dispersion shifted with aeff70-80 μm2and slope of dispersion 0,130 PS/km/nm2or less, you must fulfill the conditions mentioned below:
7x8,
0,1y0,16,
y(-0,016 x+0,21) and
0,6%11,2%.

And in order to obtain an optical fiber with dispersion shifted with aeff= 75-85 μm2and slope of dispersion is 0.135 PS/km/nm2or less, must comply with the terms mentioned below:
7x8,5,
0,1y0,16,
(-0,02 x+0,26)y(-0,02 x+0,32) and
0,6%11,2%.

On the other hand, when the wavelength of zero dispersion is on the edge of the short wavelengths of the wavelength range, restrictions mentioned below.

In particular, for that is and 0,110 PS/km/nm2or less, must comply with the terms mentioned below:
5x8,
0,12y0,22
(-0,02 x+0,24)y(-0,02 x+0,34) and
0,6%11,2%.

In this case, when x is large and y is small, even if x (r2/r1) and (2/1) satisfy the above ranges, you must install the1 at a great value. As a result, there is a possibility that transmission losses will increase due to the increase of the Rayleigh losses.

In order to prevent all kinds of accidents, limit1. That is, when1 set within the range mentioned above, the resulting transmission loss in practice are not a problem. For the same reason, use restrictions1 mentioned below.

In order to obtain an optical fiber with dispersion shifted with aeff= 70-80 μm2and slope of dispersion 0,115 PS/km/nm2f">8,
0,12y0,20,
(-0,02 x+0,25)y(-0,02 x+0.33) and
0,6%11,2%.

In order to obtain an optical fiber with dispersion shifted with aeff= 75-85 μm2and slope of dispersion 0,125 PS/km/nm2or less, must comply with the terms below:
6x8,
0,12y0,20,
(-0,02 x+0,26)y(-0,02 x+0,35) and
0,6%11,2%.

Does not require proof that the specific numerical values of r1, r2,1 and2 must also be adjusted within the ranges mentioned above, depending on such factors as the used wavelength range and installation conditions for the wavelength of zero dispersion.

Below are examples of calculations with a detailed description.

In tables 8 and 9 shows the structural parameters and characteristic values for optical fibers with offset �ttp://img.russianpatents.com/chr/955.gif">C- wavelength cutoff and DMP - diameter mode field.

Optical fiber with dispersion shifted, numbered 1 through 9 in table 8, indicated so that when the wavelength of 1550 nm, the value of the chromatic dispersion was negative, about -2 PS/km/nm, with wavelength zero dispersion approximately 1565 nm or more and the wavelength of zero dispersion at the edge of the long wavelengths of the used wavelength range.

1-3 represent examples of calculations of optical fibers with dispersion shifted witheffabout 70 μm2. All of these optical fibers with dispersion shifted satisfy the preferred conditions of the structural parameters mentioned earlier. The obtained value of the slope of the dispersion 0,125 PS/km/nm2or less.

4-6 show examples of calculations of optical fibers with dispersion shifted witheffabout 75 μm2. The obtained value of the slope of the dispersion 0,130 PS/km/nm2or less.

7-9 represent examples of calculations of optical fibers with dispersion shifted witheffabout 80 μm2. The obtained value of the dispersion slope is 0.135 PS/km/nm2or less.

10-18, are presented in table 9, the olo 2 PS/km/nm, wavelength zero dispersion is approximately 1540 nm or less and the wavelength zero dispersion is on the edge of the short wavelength of the used wavelengths (wavelength range).

10-12 represent examples of calculations of optical fibers with dispersion shifted witheffabout 70 μm2. The obtained value of the slope of the dispersion 0,110 PS/km/nm2or less.

13-15 represent examples of calculations of optical fibers with dispersion shifted witheffabout 75 μm2. The obtained value of the slope of the dispersion 0,115 PS/km/nm2or less.

16-18 represent examples of calculations of optical fibers with dispersion shifted witheffabout 80 μm2. The obtained value of the slope of the dispersion 0,125 PS/km/nm2or less.

In this embodiment, the value of the chromatic dispersion for the wavelength range is controlled within a certain range, is never equal to zero, andeffincreases. Therefore, practically do not occur nonlinear optical effects, which allows to provide the optical fiber with an offset dispersion, suitable for long-distance communication systems such as optical amplification pet dispersion can be controlled so that so he was a little boy, and when this becomes possible application in multiplexed transmission separation by wavelength.

Moreover, because the value of the chromatic dispersion can be adjusted in the direction of positive or negative values, the sign of the value of the chromatic dispersion can be installed depending on the system optical connection.

INDUSTRIAL APPLICABILITY
On the basis of the present invention obtained optical fiber dispersion-shifted, which provided that an optical fiber with an offset variance is essentially single-mode and loss curves are supported up to 100 dB/m or less, it is possible to satisfactorily implement the increase Andeffand the reduction of dispersion slope.

In addition, the structure of optical fibers with shifted dispersion of the present invention is simple, resulting in possible to effectively manufacture the optical fiber dispersion-shifted, which exhibits stable characteristics.


Claims

1. Optical fiber with an offset dispersion having the form of a distribution of refractive index, containing the Central part serdtsevidtsi r2, which is made around the Central part, while the refractive index of the Central part has a refractive index higher than the refractive index of the second part, and a shell with a lower refractive index than that of the second side core with a low refractive index, which is made around the outer periphery of the second side core with a low refractive index, characterized in that the optical fiber with an offset variance is used in the range of wavelengths of 1490...1625 nm, the effective area of the core Andeff= 45...90 μm2the slope of the dispersion 0,05 0,14...PS/km/nm2losses at bends 100 dB/m or less and a value of the chromatic dispersion -0,5...-8,0 PS/km/nm or +0,05... +10,0 PS/km/nm and has such a wavelength cutoff at which essentially implements a single-mode distribution.

2. Optical fiber with dispersion shifted under item 1, characterized in that the ratio r2/r1=4...12, i.e. with a large core diameter, and the above-mentioned optical fiber with an offset variance is used in the range of wavelengths of 1490...1625 nm Andeff=45...70 μm2the dispersion slope of 0.05... of 0.08 PS/km/nm2losses at bends 100 dB/m or less, and the value of the chromatic disperse the wound.

3. Optical fiber with dispersion shifted under item 2, characterized in that when the radius of the Central part of the core is expressed as r1, the radius of the second part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the farthest from the center of the shell is selected as a reference, as1, and the relative difference between the refractive indices of the stepped part of the core as2, r2/r1=4...12,2/1 =0,05 0,15...and1=...0,85 0,55%.

4. Optical fiber with dispersion shifted under item 2, wherein the shell includes a first shell made around the outer periphery of the stepped portion of the core, and a second shell having a higher refractive index than that of the first shell made around the outer periphery of the first shell.

5. Optical fiber with dispersion shifted under item 4, wherein, when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core is expressed as r2, the radius of the first shell as r3, the relative difference between the refractive indices of the Central part chr/916.gif">1, the relative difference between the refractive indices of the stepped part of the core - as2 and the relative difference between the refractive indices of the first shell as3, r2/r1=4...12,2/1 =0,05 0,15...,1=...0,85 0,55%,3=-0,3...0% and (r3-r2)/r1=0,2...4,0.

6. Optical fiber with dispersion shifted under item 1, characterized in that the ratio r2/r1=4...12, i.e. with a large core diameter, the optical fiber with an offset variance is used in the range of wavelengths of 1490. . . 1625 nm Andeff= 45. . .70 μm2the slope of the dispersion 0,075 0,05...PS/km/nm2losses at bends 100 dB/m or less and a value of chromatic dispersion is +0.05. . . +10,0 PS/km/nm, and has such a wavelength cutoff at which essentially implements a single-mode distribution.

7. Optical fiber with dispersion shifted under item 6, characterized in that when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the farthest from the center of the shell is selected as a reference, as2, r2/r1=4...12,1=0,55 0,75...% and2/1 0,05 0,15....

8. Optical fiber with dispersion shifted under item 6 or 7, wherein the shell includes a first shell made around the outer periphery of the stepped portion of the core, and a second shell made around the outer periphery of the first shell.

9. Optical fiber with dispersion shifted under item 8, characterized in that when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the radius of the first shell as r3, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the second shell is selected as a reference, as1, the relative difference between the refractive indices of the stepped part of the core - as2 and the relative difference between the refractive indices of the first shell as3, r2/r1= 4. . . 12,1=0,55 0,75...%,2/1=0,05 0,15...,3=-0,1...0%, and (r3-r2)/r1=0,2...4,0.

10. Optical fiber with dispersion shifted under item 1, characterized in that the solution for municipolitetom the wavelength range 1490-1625 nm Andeff=65...95 μm2the slope of the dispersion 0,08 0,14...PS/km/nm2losses at bends 100 dB/m or less and the absolute value of the chromatic dispersion of 0.5-8.0 PS/km/nm and has such a wavelength cutoff at which essentially implements a single-mode distribution.

11. Optical fiber with dispersion shifted under item 10, characterized in that when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the shell is selected as a reference, as1, the relative difference between the refractive indices of the stepped part of the core - as2, r2/r1 as x and2/1 like, 5x10; 0,080.22 and 0.6% of11,2%.

12. Optical fiber with dispersion shifted under item 10, characterized in that it has a zero dispersion wavelength in the range of long wavelengths in contrast to the used wavelength range.

13. Optical fiber , is the range of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the shell is selected as a reference, as1, the relative difference between the refractive indices of the stepped part of the core as2, r2/r1 as x and2/1 like, 6x7, with 0.10,18,(-0,02 x + 0,24), 0,6%11.2%, Andeff=65...75 μm2and the slope of the dispersion 0,125 PS/km/nm2or less.

14. Optical fiber with dispersion shifted under item 12, characterized in that when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the shell is selected as a reference, as1, the relative difference between the refractive indices of the stepped part of the core as2, r2/r1 as x and2/0,16,(-0,016 x + 0,21), 0,6%11.2%, Andeff=70...80 μm2and the slope of the dispersion 0,130 PS/km/nm2or less.

15. Optical fiber with dispersion shifted under item 12, characterized in that when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the shell is selected as a reference, as1, the relative difference between the refractive indices of the stepped part of the core as2, r2/r1 as x and2/1, 7x8,5, 0,10,16, (-0,02 x+0,26)(-0,02 x+0,32), 0,6%11,2%,
Aeff=75...85 μm2and the slope of the dispersion is 0.135 PS/km/nm2or less.

16. Optical fiber with dispersion shifted under item 10, characterized in that has zero dispersion in the range of short wavelengths in which seesa fact, when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the shell is selected as a reference, as1, the relative difference between the refractive indices of the stepped part of the core as2, r2/r1 as x and2/1 like, 5x8, 0,120,22, (-0,02 x+0,24)(-0,02 x+0,34), 0,6%11.2%, Andeff= 65...75 μm2and the slope of the dispersion 0,110 PS/km/nm2or less.

18. Optical fiber with dispersion shifted under item 16, characterized in that when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the shell is selected as a reference, as1, the relative difference between the refractive indices of stupenchatoi, 5,5x8, 0,120,20, (-0,02 x+0,25)(-0,02 x+0,33), 0,6%11,2%,
Andeff=70...80 μm2and the slope of the dispersion 0,115 PS/km/nm2or less.

19. Optical fiber with dispersion shifted under item 16, characterized in that when the radius of the Central part of the core is expressed as r1, the radius of the stepped part of the core as r2, the relative difference between the refractive indices of the Central part of the core, when the refractive index of the shell is selected as a reference, as1, the relative difference between the refractive indices of the stepped part of the core as2, r2/r1 as x and2/1 like, 6x8, 0,120,20, (-0,02 x+0,26)(-0,02 x+0,35), 0,6%11.2%, Andeff= 75...85 μm2and the slope of the dispersion 0,125 PS/km/nm2or less.

PR

 

Same patents:

The invention relates to optoelectronics and used in fiber-optic communication lines

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

FIELD: optical and electronic industry; production of fiber optic components having electrooptical effect.

SUBSTANCE: the inventions are dealt with optical and electronic industry, and may be used for development engineering of transmitting systems and data processing, in which application of the fiber optic components with electrooptical effect is expedient. The fiber consists of a core, a light conducting shell, a light-absorbing shell containing light-absorbing elements and current-carrying electrodes. The method includes operations of a down-draw of separate glass rods from glasses fillets composing elements of a fiber, piling up a pack of a with the form of cross-section of a hexahedron or a square including piling of electrodes, afterstretching of preform and its pulling into a fiber with application of a polymeric coating. The invention allows to create a single-mode fiber with heightened electrooptical effect from the glasses having a Kerr constant by 1.5 order higher than one of a quartz glass, to produce fibers with the given structure of shells, cores and control electrodes at simplification of process of a drawing down of fibers.

EFFECT: the invention ensures creation of a single-mode fiber with heightened electrooptical effect, to produce fibers with the given structure of shells, cores and control electrodes, to simplify process of fibers drawing down.

13 cl, 9 dwg

FIELD: fiber-optics.

SUBSTANCE: fiber has core and cover. Fiber is made in such a way, that in case of change of radiuses of beds with different refraction coefficients, at least one optical property of core, for example, effective section of core Aeff and slant of dispersion curve, reach appropriate limit values in given range of deflections from base radius. Length of cut wave equals 1450 nm or less. Optical fibers have practically constant optical properties and allow to vary chromatic dispersion in certain limits.

EFFECT: higher efficiency.

2 cl, 14 dwg

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