Optical fiber with dispersion offset

 

The invention is used in fiber-optic communication lines (FOCL). In the first embodiment a single-mode optical fiber has a Central part of the core, a stepped portion around a Central core, the refractive index of which is less than that of the Central part of the core, and located around the stepped portion of the core shell with a refractive index lower than the stepped part of the core. The second option single-mode optical fiber has a Central part of the core, the peripheral portion around a Central core, the refractive index of which is greater than that of the Central part of the core, and located around the stepped portion of the core shell with a refractive index lower than the stepped part of the core. In the wavelength range 1490-1625 nm chromatic dispersion of the fiber is 7 - 15 PS/(kmnm), the effective area of the core is 60-150 μm2, the slope of the dispersion is not more of 0.09 PS/(kmnm2). The bending loss of 100 dB/m or less. Optical communication line includes an optical fiber with dispersion offset and fiber dispersion compensation, the compensating tilt dis Il., 6 table.

Technical field the Present invention relates to optical fiber with dispersion offset, and makes use of him alone or in combination with the optical fiber dispersion compensation, and the like on a transmission line in an optical communication system that uses fiber optic one, two or more types, and also provides for the use for transmitting light signals of high power and for transmission by multiplexing wavelength in the optical communication system of the above-mentioned types.

The prior art wavelength at which the transmission in optical fibers based on silica occurs with minimal losses, is about 1.55 μm, and typically this range of wavelengths used for transmission over long distances. In this case, as the transmission line (i.e., optical fiber) typically use fiber dispersion offset (GVA), which is designed so that in the range of wavelengths near 1.55 um values of the chromatic dispersion is small in absolute value.

In addition, in recent years, due to the need to increase optical communication, appeared optical system is camping signals high power due to the use of optical amplifiers of the type of optical fiber amplifiers, doped with erbium (OVULE). In this case, due to the high intensity optical power transmitted through the fiber, the deterioration of transmission quality due to nonlinear optical effects can be neglected.

In addition, in conventional optical communication systems use a range of wavelengths from about 1530 to 1570 nm, however, recent research has led to a further increase in transmission systems with multiplexing transmission wavelength. For example, the developed device operating in the range from 1570 to 1625 nm, and published studies relating to the range of wavelengths from 1490 to 1530 nm. Currently, these ranges of wavelengths that are actually used or even investigated, usually called in the following way. Namely, the range of 1490 to 1530 nm is called S-band; range from 1530 to 1570 nm is called the P-range and the range from 1570 to 1630 nm is called the L-band. In practice, the useful range of wavelengths (range of wavelengths) for optical communication can be marked accordingly in the range from 1490 to 1625 nm.

The nonlinear optical effect of the transmission line estimate using nonlinear constants, expressed the ins (effective cross section) of the optical fiber.

To reduce the nonlinear effect is to reduce the nonlinear constant n2/(. Since n2 is not changed significantly when the material is already selected, efforts to reduce non-linear constant, usually taken in the direction of increasing a (.

The authors of the present invention has proposed, for example, in Japanese patent application did not pass the examination, first publication (JP-A) 10-62640, 10-2932225 and other fiber dispersion offset, the effective cross section which is significantly greater than traditional fiber with dispersion offset as a fiber with dispersion offset designed for long-distance communication systems and transmission by multiplexing wavelength.

In JP-A 11-119045 also proposed fiber dispersion offset, in which, instead of increasing the effective cross-section, the emphasis is on reducing the slope of the dispersion curve.

The slope of the dispersion curve expresses the dependence of the values of the chromatic dispersion on wavelength and is the gradient of the curve of the chromatic dispersion in construction of which is on the horizontal axis mark values of wavelength, and the vertical axis mark values of chromatic dispersion. With respect to p is INIA transmission, the greater the difference between the values of the chromatic dispersion for any two wavelengths, the less directional transfer becomes and the worse the transmission characteristics as a whole.

In addition, it was proposed fiber called VNDS (fiber non-zero dispersion shift). In WINDS, due to the fact that at the zero value of the chromatic dispersion conditions are created for four-wave mixing, which is one of the nonlinear effects, the values of the chromatic dispersion install, though small in absolute value, but not zero.

In Fig.5A-5C show examples of configurations of the distribution of the refractive index (i.e. the profile of the refractive index) used in WINDS and traditionally offer the fibers with the dispersion offset.

In Fig.5A shows an example of the profile of the refractive index type core dual forms (manual type). The core 4 consists of the Central part 1 of the core and a stepped portion 2 of the core surrounding the Central portion 1 of the core and having a lower refractive index compared with the Central part 1 of the core. In addition, around the core 4 is the shell 7, the refractive index of which is lower h the new core. The core 24 is composed of a Central part 21 of a core with a high refractive index and the intermediate part 22 with a low refractive index, located around the Central part 21 of the core. In addition, around the intermediate portion 22 of the core is annular part 23 of the core, the refractive index of which is lower than that of the Central part 21 of the core, but higher than that of the intermediate portion 22 of the core. In addition, around the annular part 23 of the core is a shell 27, which consists of the first shell 25, the refractive index of which is lower than the intermediate part 22 and the second shell 26, the refractive index which is higher than that of the first shell 25, but less than the intermediate part 22.

In Fig. 5C shows an example of the profile of the refractive index of O-type (i.e., convex type). The core 34 has a two-layer structure and consists of the Central part 31 of the core with low refractive index and a peripheral portion 32 of the core with high refractive index, located around the Central part 31 of the core. The three-layer structure (containing shell 37) profile of refractive index is formed by placing around the core 34 of the shell 37, the indicator pelseneer and the like, with such profiles of the refractive index, have advantages in terms of system design, associated with the transmission rate and the accumulated dispersion (chromatic dispersion accumulated in the transfer process) when transmitting over long distances, because of the small values of the chromatic dispersion in the range of wavelengths (the working range of wavelengths).

Setting a negative value of the chromatic dispersion, it is possible to build a system that is relatively easy to compensate for the value of the chromatic dispersion by combining the use of conventional single-mode optical fiber, calculated at 1.3 μm (1,3 OMV).

Single-mode optical fiber for 1.3 μm has a wavelength zero dispersion (i.e., the wavelength at which the value of the chromatic dispersion is zero) equal to approximately 1.3 μm, and is still widely used. In the range around 1.55 um it has a relatively high positive value of the chromatic dispersion (for example, slightly less than 17 PS/(kmnm)). This makes it possible to reduce the chromatic dispersion of the whole system by attaching a single-mode optical fiber for 1.3 μm to the output of concisely negative chromatic dispersion, accumulated during transmission through the fiber with dispersion offset due to the positive chromatic dispersion in single-mode optical fiber for 1.3 μm.

However, since traditionally offer fiber with dispersion offset and the like are used as conventional transmission lines, they must have low chromatic dispersion. For example, in many cases, the value of the chromatic dispersion at wavelengths close to 1550 nm, less than or equal to the absolute value of 6 PS/(kmnm), but with such a small absolute value is the value of the chromatic dispersion difficulties in the simultaneous increase of the effective cross section and the lower slope of the dispersion curve.

For example, when trying to sufficiently increase the effective cross-section cannot sufficiently reduce the slope of the dispersion curve, and when a significant reduction in the slope of the dispersion curve is unable to sufficiently increase the effective cross-section.

However, in recent times, according to, for example, JP-A 6-11620, was proposed system, which uses fiber dispersion compensation (refer below abbreviated as EVA), low chromatic dispersion.

In this system, the transfer is made fiber (the transmitting fiber), which is the main part of the transmission line and in the used range of wavelengths, has a relatively high value of the chromatic dispersion, and to the output end of the transmitting fiber is attached a relatively short period of EVA.

The value of the chromatic dispersion that the KJV differs from the value of the chromatic dispersion of the transmission fiber and the absolute value significantly exceeds the value of the chromatic dispersion of the transmission fiber. Thus, using the output end of the transmitting fiber, for example, short EVA, it is possible to compensate chromatic dispersion generated in the transmitting fiber for several kilometers or more, and, thus, reduce the value of the chromatic dispersion of the whole system.

In particular, if, for example, a value of the chromatic dispersion of the transmission fiber is positive, its output end connected EVA with a large absolute value of the negative value of the chromatic dispersion.

In addition, it was suggested that fiber dispersion compensation, the compensating slope of the dispersion curve (hereinafter referred to as p is the slope of the dispersion curve, that allows you to simultaneously compensate for chromatic dispersion and dispersion slope of the curve. WCDKN has the same scope, as the KJV, and it is particularly preferable to use when performing transmission by multiplexing wavelength.

On transmission lines, which are shared WCDKN and above the transmitting fiber, the local increase in the value of the chromatic dispersion can effectively suppress the generation of four-wave mixing, and, due to the almost flat curve of the chromatic dispersion on the optical system as a whole, this transmission line has a huge advantage in terms of transmission losses, and is currently being developed.

Currently, as the transmitting fiber systems using EVA or WCDKN typically use single-mode optical fiber for 1.3 μm.

In Fig. 5D shows a typical profile of the refractive index single-mode optical fiber for 1.3 μm. The profile of the refractive index tropinovogo type formed by a core 44 with a single-layer structure and the shell 47 with a single-layer structure located around the core 44.

However, if a conventional single-mode is about 80 μm2and the slope of the dispersion curve around to 0.06 PS/(nm2km), described above, but the value of the chromatic dispersion in this area will be about 17 PS/(kmnm), which is quite a lot. Therefore, given the value of the chromatic dispersion accumulated as the distribution of the optical signal, there is the problem of limitation of transmission distance.

In addition, due to the large transmission losses, and small effective cross-section EVA and WCDKN compared with conventional single-mode optical fiber for 1.3 μm, there is a strong nonlinear optical effect. Accordingly, there arises a problem of deterioration of the transmission characteristics for the system as a whole by increasing the used length.

The value of chromatic dispersion in single-mode optical fiber for 1.3 μm, with the profile of the refractive index tropinovogo type, can be reduced by adjusting the structural parameters, such as core diameter, the difference between the relative refractive indices of the shell and core, etc., However, reduce the value of the chromatic dispersion within the resulting requirements to the transmission line relative to the losses on ishibuchi effects. This limits the use of single-mode optical fiber for 1.3 μm with the profile of the refractive index tropinovogo type in an optical communication system that uses light high power.

The present invention takes the above circumstances, and its objective is to provide technology to achieve, individually or jointly, reduce costs, and improve transmission performance of optical communication systems using optical fibers of one, two or more types.

In particular, the present invention is to provide an optical fiber with dispersion offset, allowing, for example, to solve the above problem of the simultaneous decrease of the slope of the dispersion characteristics and increasing the effective cross-section of traditional VNDS and take advantage of traditional WINDS associated with a low probability of occurrence of four-wave mixing and allowing to improve transmission characteristics by suppressing the nonlinear optical effect by increasing the effective cross-section, and to achieve improvement of the transmission characteristics when performing transmission by multiplexing on lipitoronline optical fiber with dispersion offset which can be used as the transmitting fibers instead of a single-mode optical fiber for 1.3 μm, traditionally used in optical systems using EVA or WCDKN, and which has the advantage that the value of the chromatic dispersion is smaller in absolute value than the single-mode optical fiber for 1.3 μm, thanks to its chromatic dispersion can be compensated for in a short EVA or WCDKN. Another objective of the present invention is to provide an optical fiber with dispersion offset that, having the above characteristics, in addition, allows to suppress nonlinear optical effects of the transmitting fiber due to the large effective cross-section, and which can be used in the transmission by multiplexing wavelength, due to the small slope of the dispersion curve.

Another objective of the present invention is to provide an optical fiber with dispersion offset, with, if possible, a simple structure that reduces the cost of production.

Disclosure of the invention According to the present invention uses the profile indicator preliminaries fiber with dispersion offset. As described above, the optical fiber with the dispersion offset with these profiles of the refractive index were tested, mainly in relation to the setting values of the chromatic dispersion in the range of 1550 nm, as close as possible to zero.

The authors of the present invention assumed that the suppression of four-wave mixing due to higher values of the chromatic dispersion compared with the corresponding value for traditional WINDS, and the ability to simultaneously increasing the effective cross-section and reduce the slope of the dispersion curve would be useful in systems with multiplexing wavelength. They also assume that, if it is possible to obtain an optical fiber, the value of the chromatic dispersion of which is less than that of the single-mode optical fiber for 1.3 μm used in the system with multiplexing wavelength, operating in the range around 1.55 um, in combination with EVA or WCDKN, you could create a system designed for even faster gear on longer distances. In addition, if the effective cross section of the optical fiber of this type was greater than that of single-mode optical fiber for 1.3 the annual optical fiber for 1.3 μm.

Therefore, the authors of the present invention have conducted studies with the specific aim to get a small slope of the dispersion curve and more (that still has not been achieved in conventional optical fiber for transmission, the multiplexed wavelength, by setting the values of the chromatic dispersion higher than traditional WINDS, and lower than that of single-mode optical fiber for 1.3 μm.

The authors present invention also found that, in the above-described profile of the refractive index can be obtained one of the following 1) or 2) by setting the values of the chromatic dispersion between 7 and 15 PS/(kmnm).

1. WINDS, allowing to reduce the slope of the dispersion curve and to increase the effective cross-section.

2. Optical fiber with dispersion offset, the effective cross-section which is greater than that of single-mode optical fiber for 1.3 μm.

In case 1 there is a possibility to simultaneously achieve reduction of the slope of the dispersion curve and increasing the effective cross-section that is impossible for traditional VNDS. In addition, in this optical fiber with dispersion offset wavelength zero dispersion see what kerovnian wavelength, not only in the C-band and L-band and S-band, and to get this effect, which is unattainable in the case of traditional VNDS.

In case 2, the obtained fiber is particularly effective as a transmission line used in conjunction with EVA or WCDKN. In addition, due to lower values of the chromatic dispersion in comparison with the single-mode optical fiber for 1.3 μm, it is effective in the system of high-speed transmission. Due to its large effective cross-section it also allows you to reduce the nonlinear effect and therefore is effective in transmission systems for very long distances, for example, in transmission systems seabed.

In both the above cases there is a possibility to set the slope of the dispersion curve is not in excess of 0.09 PS/(kmnm2or not in excess of 0.07 PS/(kmnm2), depending on the design. Accordingly, the value of the chromatic dispersion varies slightly with wavelength, which is the ideal condition for transmission system with multiplexing wavelength.

Below, we offer specific solutions to these problems.

The first aspect of the present from the used range of wavelengths, allocated between 1490 and 1625 nm, the values of the chromatic dispersion from 7 to 15 PS/(kmnm), the effective cross-section of from 60 to 150 μm2the slope of the dispersion curve is not more of 0.09 PS/(kmnm2), losses in the bends of not more than 100 dB/m and the wavelength cutoff, which provides virtually single-mode transmission.

The second aspect of the present invention provides an optical fiber with dispersion offset corresponding to the first aspect, characterized in that the optical fiber with the dispersion offset has the profile of the refractive index, containing the Central part of the core; a stepped portion of the core located around the Central part of the core and having a lower refractive index compared with the Central part of the core; and a shell located around the stepped portion of the core and having a lower refractive index compared to the stepped part of the core.

The third aspect of the present invention provides an optical fiber with dispersion offset corresponding to the second aspect, characterized in that it has an effective cross-section of from 60 to 110 μm2and the slope of the dispersion curve which provides an optical fiber with dispersion offset corresponding to the third aspect, characterized in that, if1 - the difference between the relative indices of refraction of the Central part of the core and2 - the difference between the relative refractive indices of the stepped part of the core, calculated with respect to the shell, r1 is the radius of the Central core and r2 is the radius of the stepped part of the core, then:1 is from 0.25 to 0.55%, r2/r1 ranges from 1.5 to 5.0 and2/1 greater than or equal to 0.025 and less than or equal to -0,06(r2/r1)+0,5.

The fifth aspect of the present invention provides an optical fiber with dispersion offset corresponding to the third aspect, characterized in that matter chromatic dispersion from 7 to 11 PS/(kmnm), the effective cross-section of from 60 to 80 μm2and the slope of the dispersion curve is not more than 0.07 PS/(kmnm2).

The sixth aspect of the present invention provides an optical fiber with dispersion offset corresponding to the fifth aspect, characterized in that, if1 - the difference of relative indicators prevalentemente part of the core, calculated with respect to the shell, r1 is the radius of the Central core and r2 is the radius of the stepped part of the core, then:1 is from 0.4 to 0.5%, r2/r1 ranges from 3.5 to 5.0 and2/1 greater than or equal to 0.025 and less than or equal to -0,06(r2/r1)+0,5.

The seventh aspect of the present invention provides an optical fiber with dispersion offset corresponding to the third aspect, characterized in that matter chromatic dispersion from 12 to 15 PS/(kmnm), the effective cross-section from 90 to 110 μm2and the slope of the dispersion curve of 0.08 PS/(kmnm2or less.

The eighth aspect of the present invention provides an optical fiber with dispersion offset corresponding to the seventh aspect, characterized in that, if1 - the difference between the relative indices of refraction of the Central part of the core and2 - the difference between the relative refractive indices of the stepped part of the core, calculated with respect to the shell, r1 is the radius of the Central core and r2 is the radius of the stepped part of the core, then:
1 greater than or equal to 0.025 and less than or equal to -0,06(r2/r1)+0,5.

The ninth aspect of the present invention provides an optical fiber with dispersion offset corresponding to the first aspect, characterized in that the optical fiber with the dispersion offset has the profile of the refractive index, containing the Central part of the core; the peripheral part of the core located around the Central part of the core and having a higher refractive index in comparison with the Central part of the core; and a shell located around the peripheral portion of the core and having a lower refractive index compared with the peripheral part of the core.

The tenth aspect of the present invention provides an optical fiber with dispersion offset corresponding to the ninth aspect, characterized in that if11 - the difference between the relative indices of refraction of the Central part of the core and12 - the difference between the relative indices of refraction of the peripheral portion of the core, calculated with respect to the shell, r11 is the radius of the Central core and r12 is the radius of perifericheskom>110,3%,
120,5%,
(12-11)1.2% and
0,912r12/r111,7.

The eleventh aspect of the present invention provides an optical fiber with dispersion offset corresponding to the ninth aspect, characterized in that it has an effective cross-section of from 70 to 100 μm2and the slope of the dispersion curve of 0.07 PS/(kmnm2or less.

The twelfth aspect of the present invention provides an optical fiber with dispersion offset corresponding to the eleventh aspect, characterized in that if11 - the difference between the relative indices of refraction of the Central part of the core and12 - the difference between the relative indices of refraction of the peripheral portion of the core, calculated with respect to the shell, r11 is the radius of the Central core and r12 is the radius of the peripheral portion of the core, when:
1,3r12/r112,5,
1112-11)1,2%,
0,912r12/r111.7 and
11=and12+b, then
'a' is expressed by the function of r12/r11, namely(r12/r11-1),
'C' ranges from 1.5 to 2.0,
'b' is expressed by the function of r12/r11, namely, 0,4(r12/r11)+e,
'e' is from 0 to 0.4.

The thirteenth aspect of the present invention provides an optical fiber with dispersion offset corresponding to the ninth aspect, characterized in that it has an effective cross-section of from 90 to 150 μm2and the slope of the dispersion curve of 0.08 PS/(kmnm2or less.

The fourteenth aspect of the present invention provides an optical fiber with dispersion offset corresponding to the thirteenth aspect, characterized in that if11 - the difference between the relative indices of refraction of the Central part of the core and12 - the difference between the relative refractive indices of the stepped part of the core, calculated with respect to the shell, r11 for the mg>r12/r112,5,
110,15%,
120,5%,
(12-11)1,2%,
1,012r12/r111,5.

The fifteenth aspect of the present invention provides an optical communication system, characterized in that it is shared:
optical fiber with dispersion offset corresponding to any of aspects 1 to 14, and
fiber dispersion compensation to compensate for the chromatic dispersion of the above-mentioned optical fiber with dispersion offset or fiber with dispersion compensation, compensating the dispersion slope of the curve, to compensate for chromatic dispersion and dispersion slope of the curve of the above-mentioned optical fiber with dispersion offset.

Brief description of drawings
Fig. 1 is a diagram showing the first example of the profile of the refractive index (i.e. the type of the double core optical fiber with dispersion offset, in accordance with the present invention.

Fig.2 - diagram, the offset in accordance with the present invention.

Fig.3 is a diagram showing an example of the profile of the refractive index of O-type (ring type), which is closer to the one that is actually used.

Fig. 4 is a graph of the dependence of the effective cross section and the slope of the dispersion curve from the values of the chromatic dispersion at a constant value losses at bends, equal to 10 dB/m, for the optical fiber with the profile of the refractive index Of the type and for the optical fiber with the profile of the refractive index tropinovogo type.

Fig. 5A-5C is a diagram showing examples of the profile of the refractive index of a conventional optical fiber with dispersion offset, and Fig.5D is a diagram showing the profile of the refractive index tropinovogo type, which is a typical profile of the refractive index for single-mode optical fiber for 1.3 μm.

Fig. 6 is a graph showing the results obtained in accordance with one of the embodiments of the optical fiber with dispersion bias, discussed in the first example.

Fig. 7 is a graph showing the results obtained in accordance with another embodiment of the optical fiber with the dispersion with the availa able scientific C with one of the embodiments of the optical fiber with dispersion offset considered in the second example.

Fig. 9 is a graph showing the results obtained in accordance with another embodiment of the optical fiber with dispersion bias, discussed in the second example.

Preferred embodiments of the invention
The useful range of wavelengths (range of wavelengths) for this optical fiber with dispersion offset represents a range of wavelengths corresponding width selected in the range from 1490 to 1625 nm. No specific limitations on this account doesn't exist, so you can choose, for example, With the range from 1530 to 1570 nm, or a range of wavelengths, partially overlapping with the L-band, for example, from 1530 to 1600 nm.

The value of the chromatic dispersion in the range of wavelengths set from 7 to 15 PS/(kmnm).

Within from 7 to 12 PS/(kmnm), you can get a higher performance compared with traditional VNDS. In particular, at higher values of the chromatic dispersion than in the case of traditional WINDS, the conditions for the occurrence of four-wave mixing additionally deteriorate, and you can simultaneously is raimunda.

Within 12 to 15 PS/(kmnm), you can get a higher performance compared with single-mode optical fiber for 1.3 μm. In particular, lower values of the chromatic dispersion than in the case of conventional single-mode optical fiber for 1.3 μm, taking into account the transmission rate and the accumulated dispersion caused by transmission over long distances, give advantages from the point of view of system design. In addition, given the need to suppress nonlinear optical effect, it is advantageous, if possible, to increase the effective cross-section.

Effective cross section (can be found by the following formula.


where 'a' is the radius of the core, and E(a) field strength at the radius 'a'.

In this optical fiber with dispersion offset (in the range of wavelengths set in the range from 60 to 150 μm2. If you specify (in excess of 150 μm2the wavelength of the cutoff will be so great that in some cases will not guarantee odnomodovom transmission. While (<60 μm2you cannot achieve a higher performance compared with those obtained by using the optical fiber with headposition, must be 65 μm2, more preferably 70 μm2. In this case, from the viewpoint of reduction of a nonlinear optical effect, you can get better performance than when using optical fiber with the usual profile of the refractive index tropinovogo type.

As described above, it is preferable that the slope of the dispersion curve in the range of wavelengths as small as possible, and, in this example, in the range of wavelengths it is possible to achieve a small value, which is 0.09 PS/(kmnm2) or less, preferably of 0.08 PS/(kmnm2) or less and, more preferably, of 0.07 PS/(kmnm2) or less. When the slope of the dispersion curve over the 0.09 PS/(kmnm2) it is not always possible to achieve better performance than when using a conventional optical fiber with a dispersion shift at the wavelength of 1.55 um.

Value losses on the curves corresponds to the condition when used in the range of wavelengths of the curve diameter (2R) is 20 mm

Preferably, the losses in the bends were as small as possible, and, according nastoencheski received loss on the bends are not less than 0.1 dB/m Losses at bends in the used range of wavelengths greater than 100 dB/m, is unacceptable, because the optical fiber with the dispersion offset characteristic of the occurrence of transmission losses, even with a slight bend, resulting in the laying of fiber and manipulation occur excessive transmission losses.

Further, since the optical fiber with dispersion offset according to the present invention is a single mode optical fiber, the optical fiber with dispersion offset according to the present invention, should have a wavelength cutoff, which, in fact, guarantees odnomodovom transmission used in the range of wavelengths.

Usually the value of the wavelength cutoff regulate the method of 2m prescribed by CCITT (hereinafter, the method 2m). However, when put to practical use in telecommunication, single-mode transmission is possible, even if this value falls on the low end of the minimum value of the used range of wavelengths.

Accordingly, in an optical fiber with dispersion offset according to the present invention, using the method of 2m, set up such a wavelength cutoff, which beshenoi length (working length) of the optical fiber with dispersion offset. In particular, if the wavelength of the cutoff method is equal to 2m, for example, a 1.8 μm for the above long-distance communications, the range of which is higher than about 5000 m above the useful frequency range of wavelengths can be achieved sufficiently single-mode transmission.

In an optical fiber with dispersion offset according to the present invention, it is possible to use the profile of the refractive index as a type of dual core and ring type.

1. Example 1 (type dual-core)
In Fig.1 shows an example of the profile of the refractive index type dual core as the first example of the optical fiber with the dispersion offset according to the present invention.

This profile of refractive index is formed by the core 4 with the Central portion 1 of the core, a stepped portion 2 of the core, located around the Central part 1 of the core, and the shell 7 with a single-layer structure having a homogeneous index of refraction, which is located around the core 4.

The Central part 1 of the core are characterized by the highest refractive index. Manual part 2-core has a lower refractive index than the Central portion 1 of the core, and AET the radius of the Central part 1 of the core, r2 is the radius of the step 2 part of the core.1 is the difference of the relative performance of the Central part 1 of the core, calculated with respect to the refractive index of the shell 7, and2 is the difference of the relative performance of the stepped portion 2 of the core, calculated with respect to the refractive index of the shell 7.

In this example, the Central portion 1 of the core and a stepped portion 2 of the core can be formed of silica glass doped with germanium, and germanium additive designed to increase the refractive index, whereas the shell 7 may be formed of pure quartz glass.

In addition, the profile of the refractive index of the real optical fiber with dispersion-shifted boundary of each layer (i.e., the Central part 1 of the core, the peripheral portion 2 of the core and the shell 7) may not be as sharp, as shown in Fig.1, but are often blurred, what is depicted in the form of so-called "trough". It does not create any problems, because still allows you to effectively obtain the required characteristics of the optical fiber with the dispersion shift according Nam first example, (Set in the range from 60 to 110 μm2. Due to the fact that a (is in the data range, there is also the possibility to suppress the nonlinear optical effect.

In addition, in an optical fiber with dispersion offset discussed in this first example, you can relatively easily make the slope of the dispersion curve is not exceeded 0.08 PS/(kmnm2), preferably, does not exceed of 0.07 PS/(kmnm2).

In order to ensure the required optical fiber with dispersion offset according to the present invention, four structural parameter of the optical fiber with the dispersion offset1,2, r1 and r2, are considered in this first example, preferably be chosen so that they satisfy the following relations.

1 set in the range from 0.25 to 0.55%. To set the value of1, the lesser of 0.25%, it is impractical, since in this case the losses in the bends will be too great. In addition, it is difficult to maintain the value of the chromatic dispersion at the desired level or below (no more than 15 PS/(kmnm)). The EU is eff.

In addition, the r2/r1 (increase step) set in the range from 1.5 to 5.0, preferably from 2.0 to 5.0. If this ratio is less than 1.5, you will not be able to get the best performance compared to single-mode optical fiber for 1.3 μm, which has a traditional dropcopy profile of the refractive index. If it exceeds the 5.0, the wavelength cutoff is too large, which makes it impossible, in some cases, to guarantee odnomodovom transfer.

In addition,2 may vary in a fairly wide range of values depending on the r2/r1. When r2/r1 is small, the value of2 it is necessary to increase, while large r2/r12 must be reduced.

To ensure the above characteristics also preferably2/1 satisfy the following relations.

0,0252/1-0,06(r2/r1)+0,5.

When2/1 smaller 0,025 impossible to sufficiently reduce losses at bends. When2/

You can choose a combination of the above four structural parameters r1, r2,1 and2, which provides ingress characteristics mentioned above in the above-mentioned ranges of values.

Note that in this optical fiber with dispersion offset on the core radius r2 is not imposed no specific limitation, but it usually ranges from 5 to 25 microns.

The external diameter of the shell 7 (optical fiber with dispersion offset) is usually set equal to about 125 microns.

Optical fiber with dispersion offset discussed in this first example, it is possible, in the General case, depending on the values of the chromatic shift, be attributed to one type, which allows to obtain performance exceeds the specifications of most traditional WNDS that described above, or to another type, which allows to obtain performance exceeds the specifications of most single-mode optical fiber for 1.3 μm. Their description is given below.

1.1 VNDS providing both increase (and decrease the slope of the dispersion curve
In this case, the value of the chromatic dispersion is set in the range of the offered value of the chromatic dispersion traditional WINDS (less than 6 PS/(kmnm)), it is possible to achieve both the increase (and decrease the slope of the dispersion curve. Note that the offset values of the chromatic dispersion to a positive value of the chromatic dispersion provides an advantage from the viewpoint of suppression of four-wave mixing. In addition, with such values of the chromatic dispersion, the level of the accumulated dispersion at a corresponding transmission distance does not cause any problems, and, in more long-distance transmission, combining the fiber with the appropriate EVA or WCDKN, you can build a system that suppresses the residual variance.

In particular, this optical fiber with dispersion offset can be obtained (from 60 to 80 μm2and the slope of the dispersion curve is not more than 0.07 PS/(kmnm2). This enables stronger to suppress nonlinear optical effect than when using traditional WINDS, and thus to provide an optical fiber that is designed for use in transmission by multiplexing wavelength. In addition, it simplifies the establishment of a wavelength cutoff, able to guarantee odnomodovom transfer.

In this optical fiber with the dispersion sexenio 3.5 and 5.0 and2/1 - greater than or equal to 0.025 and less than or equal to minus 0.6(r2/r1)+0,5.

1.2 Optical fiber with dispersion offset that increase (to a greater extent than conventional single-mode optical fiber for 1.3 μm.

In this case, the value of the chromatic dispersion is set in the range from 12 to 15 PS/(kmnm). This allows to obtain (from 90 to 110 μm2and the slope of the dispersion curve is not more than 0.08 PS/(kmnm2). The nonlinear optical effect can also be suppressed to a greater extent than when using conventional single-mode optical fiber for 1.3 μm, which enables to provide an optical fiber that is designed for use in transmission by multiplexing wavelength.

In this optical fiber with dispersion offset it is possible to achieve better performance by setting1 from 0.4% to 0.5%, r2/r1 from 2.0 to 4.0 and2/1 not less than 0.025 and the value determined by the value not more than 0,06(r2/r1)+0,5.

Table 1 shows the simulation results representing the structural parameters and characteristics is, is AutoRAE meets the above conditions. Note that the measured wavelength equal to 1550 nm, and the symbolscand PD denote, respectively, the wavelength cutoff and the diameter of the field of fashion.

Were obtained characteristics, providing the preferred ranges of values for a (, slope of the dispersion curve, the values of the chromatic dispersion, losses at bends and wavelength cutoff.

The results are given in table. 1.

2. Example 2. O-type (ring type)
In Fig.2 shows an example of the profile of the refractive index of O-type (ring type) as a second example of the optical fiber with the dispersion offset according to the present invention.

This profile of the refractive index contains a core 34 having a two-layer structure consisting of the Central part 31 of the core with low refractive index and a peripheral portion 32 of the core with high refractive index, located around the Central part 31 of the core. The three-layer structure (containing shell 37) profile of the refractive index of the convex type formed by placing around the core 34 of the shell 37, the refractive index of which is lower than that of the peripheral portion 32 sergeanovo fluorine, moreover, fluoride additive is designed to reduce the refractive index of the peripheral portion 32 of the core is formed of silica glass doped with germanium, and the shell 37 is formed of pure quartz glass.

Pay attention to the fact that, due to the fact that it is possible to effectively obtain the required characteristics of the optical fiber with dispersion offset according to the present invention, the boundary of each layer (i.e., the Central part 31, the peripheral portion 32 and the shell 37) can be blurred, which is shown in Fig.3, but are often in the round state, which generates the so-called "deflection", the same as for example 1. Alternatively, they can be slightly modified so that the distribution of the refractive index of the peripheral portion 32 of the core represents an increase or decrease, carried out in a sequence of steps or something like that.

In Fig.4 depicts a graph showing, at a constant value losses at bends, equal to 10 dB/m, the change in the effective cross section and the slope of the dispersion curve with changing values of the chromatic dispersion is carried out by adjusting strukturalne, with the profile of the refractive index tropinovogo type.

From the graph we see that the advantage of the ring-type is that it is characterized by higher values of a (and the advantage tropinovogo type is that it is characterized by smaller values of the slope of the dispersion curve.

In addition, with decreasing values of the chromatic dispersion (i.e., when moving along the horizontal axis from left to right), ( drops sharply near 15 PS/(kmnm) and 10 PS/(kmnm), respectively, for tropinovogo type and ring type. Note that the area in which as the value of the chromatic dispersion, and (high (i.e., the range of values of the chromatic dispersion greater than about 15 PS/(kmnm) for tropinovogo type and 10 PS/(kmnm) for ring type), may not be used for practical application due to the lack of ability to obtain acceptable losses at bends and microscopic characteristics of the bends.

The slope of the dispersion curve is almost universally not affected by changes in the values of the chromatic dispersion and almost completely determined by the profile index "https://img.russianpatents.com/chr/8226.gif">nm), a (for tropinovogo type equal to 58 μm2while (for ring type is 78 μm2i.e. quite large. On the contrary, while for tropinovogo type the slope of the dispersion curve is equal to approximately 0,058 PS/(kmnm2), for a ring-type slope of the dispersion curve is approximately 0,068 PS/(kmnm2), i.e., is large enough. This ring type exceeds dropcopy type at 35% (and 17% by the slope of the dispersion curve. Accordingly, the o-ring type is quite different from tropinovogo type of speed increase (and the slope of the dispersion curve. In addition, as the speed increases (for ring-type higher than for tropinovogo type, although the slope of the dispersion curve is rather large, circular type, in General, gives a greater advantage, as it provides all of the desirable characteristics that should be possessed by the transmission line, including a decrease in the value of the chromatic dispersion, the increase (and decrease the slope of the dispersion curve.

In addition, if we consider the slope of the dispersion curve and the value of the chromatic dispersion at a (equal to 80 μmfor tropinovogo type. On the contrary, the value of the chromatic dispersion for ring-type approximately 35% less than the value of the chromatic dispersion for tropinovogo type. Accordingly, although the slope of the dispersion curve for a ring-type some-more than tropinovogo type, the effect of reducing the value of the chromatic dispersion for the ring type is stronger and, therefore, from this point of view, ring type, in General, preferred for transmission lines in comparison with odnopoloi type.

Accordingly, as described above, if the focus is only on the slope of the dispersion curve, the slope of the dispersion curve for tropinovogo type less, and because this type is more preferable, however, because the effect of increasing (and decreasing values of the chromatic dispersion is more pronounced in the case of a ring-type, this type provides, in General, more favorable characteristics than dropcopy type.

In an optical fiber with dispersion bias, discussed in example 2, to obtain preferable characteristics, namely, the values of the chromatic dispersion, (, slope of the dispersion curve and wavelength cutoff, four structural parameter,11,

11 set less than or equal to 0.3%. The excess values of 0.3% would mean an approximation to the profile of the refractive index tropinovogo type, making it difficult to sufficiently increase a (.

12 set greater than or equal to 0.5% and12-11 - less than or equal to 1.2%. If these conditions are not met, you cannot install losses at bends in the above range, the wavelength cutoff becomes too large, and the resulting fiber is unusable.

Preferably also, to run ratio of 0.912r12/r111,7. If this value is less than 0.9, it is impossible to set the loss at bends or wavelength cutoff in the used ranges. If it exceeds the 1.7, difficulties arise with increasing a (. In addition, when designing op the parameters r11, r1211 and12, which provides ingress characteristics mentioned above in the above-mentioned ranges of values.

Note that in this optical fiber with dispersion offset r12, i.e., the radius of the core, while not subject to any specific restrictions, however, is usually from 2 to 6 microns.

The external diameter of the shell 37 (optical fiber with dispersion offset) is usually set equal to approximately 125 microns.

In addition, in an optical fiber with dispersion bias, discussed in example 2, to obtain characteristics (from 70 to 100 μm2and the slope of the dispersion curve is not more than 0.07 PS/(kmnm2), it is preferable that the structural parameters were set so as not only to provide the above-mentioned ranges of values of r12/r11,11,12,12-11,12r12/r11, but also to ensure that the following conditions are met:
When11 = a12+b,
'a' is expressed by the function of r12/r11, namelyr12/r11)+e,
'e' is from 0 to 0.4.

In addition, to obtain characteristics (from 90 to 150 μm2and the slope of the dispersion curve is not more than 0.08 PS/(kmnm2), it is preferable that the structural parameters were set so that the following requirements are met:
1,3r12/r112,5,
110,15%,
120,5%,
(12-11)1,2%,
1,012r12/r111,5.

Table 2 shows the simulation results, demonstrating the structural parameters and characteristic values corresponding to the example of a specific structure of the first optical fiber with dispersion offset that meets the above conditions. Note that the measured wavelength equal to 1550 nm.

Were obtained characteristics, providing the preferred ranges of values (that is the slope of the dispersion curve, the values of the chromatic dispersion, losses at bends and wavelength cutoff.

Optical and, for example, by chemical vapor deposition from the vapor phase method or axial deposition from the vapor phase.

Since these optical fiber with dispersion offset are relatively simple profiles of the refractive index, the number of structural parameters that can be managed in the course of manufacture, is small, which is advantageous from a manufacturing point of view and allows you to effectively obtain the desired characteristics.

Embodiments of the
The results of the present invention are presented below in relation to specific variants of implementation.

In Fig. 6 and table 3 shows the results corresponding to a variant of implementation of the optical fiber with dispersion bias, discussed in the first example. According to this variant implementation, the optical fiber with the dispersion offset were made by the method of axial deposition from the vapor phase on the basis of design conditions of test samples 1 and 5, are presented in table 1. As a result, according to the first variant of implementation, the C-band, selected from a range 1490-1625 nm, were obtained values of the chromatic dispersion of +7 to +11 PS/(kmnm). In addition, since probate, the value of the chromatic dispersion is sufficient to perform a transmission by multiplexing a wavelength in the S-band. Moreover, due to the smallness of the slope of the dispersion curve, it was confirmed that the value of the chromatic dispersion in the L-band has also been reduced to the proper degree.

In Fig. 7 and table 4 shows the results of another variant implementation of the optical fiber with dispersion bias, discussed in the first example. According to this variant implementation, the optical fiber with the dispersion offset were made by the method of axial deposition from the vapor phase on the basis of design conditions test samples 14 and 16 shown in table 1. As a result, were obtained characteristics are almost identical design. In addition, it was provided with a (not less than in the case of single-mode optical fiber for 1.3 μm and in the range of wavelengths selected from the above-mentioned range (C-band, according to a variant of implementation), was obtained the value of the chromatic dispersion between +12 and +15 PS/(kmnm) which is less than the values obtained for single-mode optical fiber for 1.3 μm.

Fig. - Christ.tion, considered in the second example. According to this variant implementation, the optical fiber with the dispersion offset were made by the MCVD method based on the design conditions of test sample 1 shown in table 2. The profile of the refractive index was blurred, however, were obtained characteristic values are virtually the same design. In addition, the range of wavelengths selected from the above-mentioned range (C-band, according to a variant of implementation), was obtained the value of the chromatic dispersion between +7 and +11 PS/(kmnm), similarly to variant implementation, shown in Fig.6 and in table 3.

In Fig. 9 and table 6 shows the results of another variant implementation of the optical fiber with dispersion bias, discussed in the second example. According to this variant implementation, the optical fiber with the dispersion offset were made by the MCVD method based on the design conditions of the test sample 4 shown in table 2. As a result, it was confirmed that a (about 30% more than in the case of single-mode optical fiber for 1.3 μm, and the value of the chromatic dispersion is reduced by approximately nnnam offset considered in example 1 or 2, the values of the chromatic dispersion in the range of wavelengths allocated between 1490 and 1625 microns, less than in the case of conventional single-mode optical fiber for 1.3 μm, in an optical communication system, where the optical fiber with dispersion bias, discussed in example 1 or 2, is used in conjunction with EVA or WCDKN, it is possible to make the length of the EVA or WCDKN shorter than in conventional single-mode optical fiber for 1.3 μm.

In addition, a large (optical fiber with dispersion offset allows to suppress nonlinear optical effects and to improve transmission characteristics, resulting in this optical fiber with dispersion offset is ideal for transmitting light signals of high power. In addition, thanks to the small slope of the dispersion curve, it is intended for transmission by multiplexing wavelength.

Although the KJV or WCDKN not imposed no specific limitation, however, you can use an existing model with the profile of the refractive index of the so-called W-type or W-type with a segmented core.

Industrial application
According to the range of wavelengths, allocated between 1490 and 1625 microns, less than in the case of conventional single-mode optical fiber for 1.3 μm, in an optical communication system, where the optical fiber with the dispersion offset that meets the present invention is used in conjunction with EVA or WCDKN, it is possible to make the length of the EVA or WCDKN shorter than in conventional single-mode optical fiber for 1.3 μm. This allows to reduce system cost and improve transmission characteristics.

In addition, a large (optical fiber with dispersion offset allows to suppress nonlinear optical effects and to improve transmission characteristics, resulting in this optical fiber with dispersion offset is ideal for transmitting light signals of high power. In addition, thanks to the small slope of the dispersion curve, it is suitable for transmission by multiplexing wavelength.

In addition, since the profile of the refractive index of the optical fiber with the dispersion offset is relatively simple, the number of structural parameters that can be managed in the course of manufacture, is small, which is advantageous from the point of view of production and allows effective the fiber dispersion offset having used a range of wavelengths allocated between 1490 and 1625 nm, the values of the chromatic dispersion 7-15 PS/(kmnm), the effective cross-section of 60-150 μm2the slope of the dispersion curve is not more of 0.09 PS/(kmnm2), losses in the bends of not more than 100 dB/m and the wavelength cutoff, which provides virtually single-mode transmission, but such optical fiber has a profile of refractive index and contains the Central part of the core, a stepped portion of the core located around the Central part of the core and having a lower refractive index compared with the Central part of the core, and a shell located around the stepped portion of the core and having a lower refractive index compared to the stepped part of the core.

2. Optical fiber with dispersion offset by p. 1, characterized in that it has an effective cross-section 60-110 μm2and the slope of the dispersion curve is not more than 0.08 PS/(kmnm2).

3. Optical fiber with dispersion offset by p. 2, characterized in that, if1 - the difference between the relative indices of refraction of the center is the part of the core, calculated with respect to the shell, r1 is the radius of the Central core and r2 is the radius of the stepped part of the core, then1 is 0,25-0,55%, r2/r1 is 1.5-5.0 and2/1 greater than or equal to 0.025 and less than or equal to -0,06(r2/r1)+0,5.

4. Optical fiber with dispersion offset by p. 2, characterized in that matter chromatic dispersion 7-11 PS/(kmnm), the effective cross-section of 60-80 μm2and the slope of the dispersion curve is not more than 0.07 PS/(kmnm2).

5. Optical fiber with dispersion offset p. 4, characterized in that, if1 - the difference between the relative indices of refraction of the Central part of the core and2 - the difference between the relative refractive indices of the stepped part of the core, calculated with respect to the shell, r1 is the radius of the Central core and r2 is the radius of the stepped part of the core, then1 is 0,4-0,5%, r2/r1 is 3.5-5.0 and2/1 greater than or equal to 0.025 and less than or equal to -0,06(r2/r1)+0,5.

6. The optical fiber is 12-15 PS/(kmnm), the effective cross-section of 90-110 μm2and the slope of the dispersion curve is not more than 0.08 PS/(kmnm2).

7. Optical fiber with dispersion offset by p. 6, characterized in that, if1 - the difference between the relative indices of refraction of the Central part of the core and2 - the difference between the relative refractive indices of the stepped part of the core, calculated with respect to the shell, r1 is the radius of the Central core and r2 is the radius of the stepped part of the core, then1 is 0,4-0,5%, r2/r1 is 2.0-4.0 and2/1 greater than or equal to 0.025 and less than or equal to -0,06(r2/r1)+0,5.

8. Optical fiber with dispersion offset, having used the range of wavelengths allocated between 1490 and 1625 nm, the values of the chromatic dispersion 7-15 PS/(kmnm), the effective cross-section of 60-150 μm2the slope of the dispersion curve is not more of 0.09 PS/(kmnm2), losses in the bends of not more than 100 dB/m and the wavelength cutoff, which provides virtually single-mode transmission, but such optical fiber ima, located around a Central core and having a higher refractive index in comparison with the Central part of the core, and a shell located around the peripheral portion of the core and having a lower refractive index compared with the peripheral part of the core.

9. Optical fiber with dispersion offset by p. 8, characterized in that if11 - the difference between the relative indices of refraction of the Central part of the core and12 - the difference between the relative indices of refraction of the peripheral portion of the core, calculated with respect to the shell, r11 is the radius of the Central core and r12 is the radius of the peripheral portion of the core,
1,3r12/r112,5,
110,3%,
120,5%,
(12-11)1,2%,
0,912r12/r111,7.

10. Optical fiber with dispersion offset by p. 8, characterized in that it is effective is p>).

11. Optical fiber with dispersion offset by p. 10, characterized in that if11 - the difference between the relative indices of refraction of the Central part of the core and12 - the difference between the relative indices of refraction of the peripheral portion of the core, calculated with respect to the shell, r11 is the radius of the Central core and r12 is the radius of the peripheral portion of the core, when
1,3r12/r112,5,
110,3%,
120,5%,
(12-11)1,2%,
0,912r12/r111,7,
11 = a12+b,
it is expressed by the function of r12/r11, namely(r12/r11-1);
with 1,5-2,0;
b is expressed by the function of r12/r11, namely, 0,4(r12/r11)+e;
e is 0-0,4.

12. Optical fiber with dispersion offset by p. 8, characterized in that it has an effective cross-section 90 -150 μm is e fiber dispersion offset by p. 12, characterized in that if11 - the difference between the relative indices of refraction of the Central part of the core and12 - the difference between the relative refractive indices of the stepped part of the core, calculated with respect to the shell, r11 is the radius of the Central core and r12 is the radius of the peripheral portion of the core,
1,3r12/r112,5,
110,15%,
120,5%,
(12-11)1,2%,
1,012r12/r111,5.

14. Optical communication system, characterized in that it shared optical fiber with dispersion offset according to any one of paragraphs. 1-13 and fiber dispersion compensation to compensate for the chromatic dispersion of the above-mentioned optical fiber with dispersion offset or fiber with dispersion compensation, compensating the dispersion slope of the curve, to compensate for chromatic dispersion and dispersion slope of the curve above about

 

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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.

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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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