One-mode optic fiber and composition optical communication line

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

 

The scope of the invention

The present invention relates to optical fibers used in optical communication systems, and in particular, relates to an optical fiber designed for use in high speed communication systems with high throughput operating mode division multiplexing wavelength (hereinafter abbreviated MDR).

Description of the prior art

Technology MDR significantly increase the capacity of optical communication systems. For communication in the MDR mode requires the suppression of nonlinear effects and management of chromatic dispersion in an optical fiber.

In the General case, nonlinear effects in an optical fiber is denoted by the value of n2/Aeffwhere n2nonlinear refractive index of optical fiber, and aeffeffective cross - section of the core of the optical fiber. Thus, the nonlinear effects are inversely proportional Andeff. Accordingly, a variety of optical fiber such as optical fiber with a larger effective cross-section Andeffoptical fiber with a reduced slope of the dispersion curve and the optical fiber to compensate for the slope of the dispersion curve.

There are two main methods of increasing about usknow ability of the communication system, working in MDR mode. The first method is to increase the number multiplexing optical signals, and the second method is to increase the transmission speed.

The increase in the number multiplexing optical signals is carried out by expanding the range of wavelengths used for transmission. For transmission mode MDR usually use a range of 1550 nm. Within the range of 1550 nm is widely used so-called C-band (conventional band, 1530-1565 nm), but in recent years, had started to use L-band (long wavelength range, 1565-1625 nm) and S-band (short wavelength range, 1460-1530 nm).

In this regard, have been proposed various optical fibers such as optical fibers for use in the C-band and L-band optical fiber with high chromatic dispersion for use in S-, C - and L-bands.

However, the profile of the refractive index of all the traditional optical fibers designed to achieve the desired optical characteristics at a given chromatic dispersion.

On Fig depicts a graph showing characteristics of the chromatic dispersion of a typical optical fibers used in the MDR system. Optical fibers a and b having different characteristics of the chromatic dispersion implemented by f is Mirovaya different profiles of the refractive index.

A method of manufacturing an optical fiber with dispersion offset provides low level non-linear effects, disclosed in Japanese patent application did not pass the examination, first publication No. Hei 8-220362. The invention disclosed in Japanese patent application did not pass the examination, first publication No. Hei 8-220362, provides a way of constructing an optical fiber with a larger diameter field mode (hereinafter, abbreviated as "PDM") in the range of 1.55 μm. According to the reference document (Technical report IIIS, Institute of engineers in electronics, Informatics and communications, "optical communication System", OCS-94-74, from November 18, 1994)related to the above-mentioned patent application, the optical fibers with increased PDM described in the application, is characterized by the monotonic change of the chromatic dispersion and the PDM with the change of the radius of the core.

Thus, by adjusting the radius of the core using core core optical fiber having a profile of refractive index, developed according to the method proposed in the aforementioned patent application, in order chromatic dispersion differed from the predefined chromatic dispersion, it will inevitably happen a big change PDM.

When manufacturing an optical fiber according to the above method results in the reduction of the PDM optical fiber, it not only is a disadvantage from the point of view of losses at the joints, but also, at high density optical power transmitted in the optical fiber as the optical amplifiers, causes problems such as the strengthening of nonlinear effects and the deterioration of the transmission characteristics.

On the other hand, it is also necessary to reduce the slope of the dispersion curve of the optical fibers used in the MDR system. The decrease in the slope of the dispersion curve provides a small variation of chromatic dispersion in a wide range of wavelengths. It is very important for high-speed communication systems, in which the chromatic dispersion severely limits the transmission distance. In conventional optical fibers, the slope of the chromatic dispersion is usually greater than 0.05 PS/(nm2·km), whereas in high-speed communication systems are required optical fiber with the slope of the dispersion curve of 0.05 PS/(nm2·km) or less.

The invention

The present invention eliminates the above described problems, and an object of the invention is the provision of a single-mode optical fiber, the chromatic dispersion of which can be adjusted within wide limits by using a single profile of the refractive index by adjusting the radius of the core, in other words, the task invented the I is to provide optical fiber, preferably, for use in high speed communication systems with high throughput operating mode division multiplexing wavelength (MDR).

To solve this problem, the present invention provides a single-mode optical fiber containing a core and a shell, and the core contains two or more layers having different refractive indices, and at least one optical property reaches extreme values in a specific range of the radius of the core when changing the radius of the core.

The above structure makes it possible to vary the chromatic dispersion in the range required for manufacturing optical fiber with a given chromatic dispersion, based on a single profile of the refractive index single-mode optical fiber, while maintaining the optical properties.

In the above-described single-mode optical fiber, the optical property can reach extreme values within a deviation of ±10% from the base radius of the core.

In the above-described single-mode optical fiber, the optical property can reach extreme values within a deviation of ±5% from the base radius of the core.

In a single-mode optical fiber, at least one optical its the creation may depend on the chromatic dispersion, reaching extreme values.

In the above-described single-mode optical fiber, the optical property can reach extreme values in the field, covering positive and negative values of the chromatic dispersion.

In a single-mode optical fiber, the optical property can be represented as the slope of the dispersion curve.

In a single-mode optical fiber, where the optical property reaches extreme values in the field, covering positive and negative values of the chromatic dispersion, the optical property can reach extreme values in the field, covering positive and negative values of the slope of the dispersion curve.

In a single-mode optical fiber, the optical property can be an effective cross section of the core or the diameter of the field of fashion.

In a single-mode optical fiber, the slope of the dispersion curve can be not more than 0.05 PS/(nm2·km) in the working wavelength range.

In a single-mode optical fiber, the slope of the dispersion curve can be no more than 0,03 PS/(nm2·km) in the working wavelength range.

In a single-mode optical fiber, at least one of the layers with different refractive indices that make up the core may be pokazatel the refractive the smaller the refractive index of the shell.

In addition, the present invention provides a composite optical communication line, compensating for the slope of the dispersion curve by combining single-mode optical fiber in which the optical property reaches extreme values in the field, covering positive and negative values of the chromatic dispersion, and in the field, covering positive and negative values of the slope of the dispersion curve.

In the above structures, when the optical property, reaching extreme values, represents the effective cross section of the core or PDM, because changing the radius of the core does not lead to a significant change of these parameters, it is possible to suppress nonlinear effects in single-mode optical fiber.

In addition, since the manufacture of the optical fiber, in which optical property reaches extreme values in the field, covering positive and negative values of the chromatic dispersion and dispersion slope of the curve, single-mode optical fiber may differ by the signs of the values of the chromatic dispersion and dispersion slope of the curve, and, at the same time, to have almost the same optical property.

In addition, a single-mode optical fiber unite the La create a composite optical line, able to compensate for the slope of the dispersion curve.

Brief description of drawings

Figure 1 presents a diagram of the profile of the refractive index single-mode optical fiber according to the present invention.

On Figa is a diagram illustrating the calculated dependence of the chromatic dispersion of the radius of the core according to the first variant implementation of the single-mode optical fiber according to the present invention.

On FIGU is a diagram illustrating the calculated dependence of the slope of the dispersion curve of the radius of the core according to the first variant implementation of the single-mode optical fiber according to the present invention.

On Figs is a diagram illustrating the calculated dependence of the effective cross section of the core radius core according to the first variant implementation of the single-mode optical fiber according to the present invention.

On Fig.2D is a diagram illustrating the calculated dependence of the losses on the bending radius of the core according to the first variant implementation of the single-mode optical fiber according to the present invention.

On Figa is a diagram for comparison of measured values and calculated values of the effective cross-section of the core in relation to the value is the second chromatic dispersion according to the first variant implementation of the single-mode optical fiber according to the present invention.

On FIGU is a diagram for comparison of measured values and calculated values of the slope of the dispersion curve with respect to the values of the chromatic dispersion according to the first variant implementation of the single-mode optical fiber according to the present invention.

Figure 4 is a diagram of the chromatic dispersion in the working wavelength range according to the first variant implementation of the single-mode optical fiber according to the present invention.

On Figa is a diagram illustrating the calculated dependence of the chromatic dispersion of the radius of the core according to the second variant of realization of single-mode optical fiber according to the present invention.

On FIGU is a diagram illustrating the calculated dependence of the slope of the dispersion curve of the radius of the core according to the second variant of realization of single-mode optical fiber according to the present invention.

On Figs is a diagram illustrating the calculated dependence of the effective cross section of the core radius core according to the second variant of realization of single-mode optical fiber according to the present invention.

On Fig.5D is a diagram illustrating the calculated dependence of the losses on the bending radius from the heart of the ins according to the second variant of realization of single-mode optical fiber according to the present invention.

On Figa is a diagram for comparison of measured values and calculated values of the effective cross-section of the core in relation to the values of the chromatic dispersion according to the second variant of realization of single-mode optical fiber according to the present invention.

On FIGU is a diagram for comparison of measured values and calculated values of the slope of the dispersion curve with respect to the values of the chromatic dispersion according to the second variant of realization of single-mode optical fiber according to the present invention.

7 is a diagram of the chromatic dispersion in the working wavelength range according to the second variant of realization of single-mode optical fiber according to the present invention.

On Figa is a diagram illustrating the calculated dependence of the chromatic dispersion of the radius of the core according to the third variant of implementation of the single-mode optical fiber according to the present invention.

On FIGU is a diagram illustrating the calculated dependence of the slope of the dispersion curve of the radius of the core according to the third variant of implementation of the single-mode optical fiber according to the present invention.

On Figs is a diagram illustrating the calculation for aImost effective cross-section of the core radius core according to the third variant of implementation of the single-mode optical fiber according to the present invention.

On Fig.8D is a diagram illustrating the calculated dependence of the losses on the bending radius of the core according to the third variant of implementation of the single-mode optical fiber according to the present invention.

On Figa is a diagram for comparison of measured values and calculated values of the effective cross-section of the core in relation to the values of the chromatic dispersion according to the third variant of implementation of the single-mode optical fiber according to the present invention.

On FIGU is a diagram for comparison of measured values and calculated values of the slope of the dispersion curve with respect to the values of the chromatic dispersion according to the third variant of implementation of the single-mode optical fiber according to the present invention.

Figure 10 is a diagram of the chromatic dispersion in the working wavelength range according to the third variant of implementation of the single-mode optical fiber according to the present invention.

On Figa is a diagram illustrating the calculated dependence of the chromatic dispersion of the radius of the core according to the fourth variant of the implementation of the single-mode optical fiber according to the present invention.

On FIGU is a diagram illustrating calculation hung the susceptibility of the slope of the dispersion curve of the radius of the core according to the fourth variant of the implementation of the single-mode optical fiber according to the present invention.

On Figs is a diagram illustrating the calculated dependence of the effective cross section of the core radius core according to the fourth variant of the implementation of the single-mode optical fiber according to the present invention.

On Fig.11D is a diagram illustrating the calculated dependence of the losses on the bending radius of the core according to the fourth variant of the implementation of the single-mode optical fiber according to the present invention.

On Figa is a diagram for comparison of measured values and calculated values of the effective cross-section of the core in relation to the values of the chromatic dispersion according to the fourth variant of the implementation of the single-mode optical fiber according to the present invention.

On FIGU is a diagram for comparison of measured values and calculated values of the slope of the dispersion curve with respect to the values of the chromatic dispersion according to the fourth variant of the implementation of the single-mode optical fiber according to the present invention.

On Figs is a diagram for comparison of measured values and calculated values of DME in relation to the values of the chromatic dispersion according to the fourth variant of the implementation of the single-mode optical fiber according to the present izobreteny is.

On Fig is a diagram of the chromatic dispersion in the working wavelength range according to the fourth variant of the implementation of the single-mode optical fiber according to the present invention.

On Fig is a diagram of chromatic dispersion for the traditional optical fiber MDR.

A detailed description of the preferred embodiments

Proceed to the detailed explanation of the invention.

To explain the first variant implementation of the single-mode optical fiber according to the present invention refer to figure 1-4.

Single-mode optical fiber includes a core and a shell, the core contains two or more layers with different refractive indices. The first layer (the Central region of the core) is placed around a Central core. The second layer is placed around the selected first layer and the third layer (the annular region of the core) is placed around the second layer. In accordance with the present invention, the relative refractive indices of the first, second and third layers and layer shell is a Δ 1>Δ 3>Δabout>Δ 2. The second layer in the framework of this invention designated as a disaster area core”. Figure 1 shows an example of the profile of the refractive index for one is mode optical fiber.

According to figure 1, the optical fiber has a Central area 1 core, a disaster area 2 core surrounding the Central area 1 core, the annular area 3 core surrounding a disaster area 2 core, and a shell 4 surrounding annular area 3 core.

The Central area 1 core has a higher refractive index than the shell 4, and a disaster area 2 core has a lower refractive index than the shell 4, and the annular area 3 core has a higher refractive index than the refractive index of the shell.

The profile of the refractive index single-mode optical fiber is characterized by the radii of the core and the relative difference of the refractive indices, which are listed in Table 1, and calculated values of the optical properties of single-mode optical fibers are presented in Table 2.

Table 1

r2/r1r3/r1Δ1Δ2Δ3
2,02,70,53-0,100,20

Table 2

Wavelength cutoff [nm]Andeff[the km 2]PDM [µm]Chromatic dispersion [PS/(nm· km)]The slope of the dispersion curve [PS/nm2·km)]Losses at bends [dB/m]
118050,238,09+7,6+0,0460,4

Note: the values evaluated at the wavelength of 1550 nm; losses at bends ⊘ 20.

On figa-2D shows the changes in optical properties by changing the core radius of the optical fiber, the profile of the refractive index of which is presented in figure 1 and in Table 1, and figa shows the change of the chromatic dispersion at the wavelength of 1550 nm; figv shows the change in the slope of the dispersion curve at the wavelength of 1550 nm; figs shows the change in the effective cross section of the core Andeffat the wavelength of 1550 nm; and fig.2D shows the variation in losses at bends in the curve diameter ⊘ 20. The base radius of the core, pending on the x-axis is a relative value with respect to the estimated radius of the core, in this example, the basic core radius r3equal cent to 8.85 μm.

From figa-2D, it follows that, unlike chromatic dispersion and losses in the bends, which vary monotonically with changing radius, the effective cross-section of the core Andeffand the slope of disperse is authorized curve reaches the corresponding limit values near the base of the radius in the Central region of the core. Thus, by changing the radius of the core relative to the base radius of the core within ±10%, you can modify the chromatic dispersion of the optical fiber at the wavelength of 1550 nm in the range of +4~+10 PS/(nm· km), at the same time, keeping the effective cross section of the core Andeffand the slope of the dispersion curve unchanged.

The core material made in accordance with the structural parameters presented in figure 1 and in Table 1, used in the manufacture of test specimens of the optical fiber, the core radii are varied in the range of about ±10% relative to the base radius of the core, in order to evaluate their optical properties. On figa shows the change in the effective cross section of the core Andeffand figv shows the change in the slope of the dispersion curve. In both cases, the abscissa axis is delayed chromatic dispersion at the wavelength of 1550 nm. On figa, 3B bold dots And indicate the measured values for the obtained optical fiber, and the solid lines indicate calculated values. According figa, 3B, the effective cross-section of the core Andeffand the slope of the dispersion curve depends on the chromatic dispersion and reach the relevant limit values. From figa, 3B it follows that the calculated values essentially agree is consistent with the measured values, and, therefore, it is possible to make optical fibers having different values of the chromatic dispersion, but are practically the same effective cross-section of the core Andeffand the slope of the dispersion curve.

Figure 4 shows the characteristics of chromatic dispersion in optical fibers a and b, presented on figa, 3V. Optical fiber And has a chromatic dispersion over 2 PS/(nm· km) in the C-band and L-band, and optical fiber demonstrates these values in S-band, C-band and L-band, indicating its suitability for use in the MDR system.

Accordingly, a single-mode optical fiber, considered in this example, consisting of a core and a shell, the core of which consists of at least two layers with different refractive indexes can be obtained by making such optical fiber, in which at least two optical properties (for example, the effective cross-section of the core Andeffand the slope of the dispersion curve) reaches the corresponding limit values when changing the radius of the core within certain limits relative to the base radius that allows to realize a single-mode optical fiber on the basis of a single profile of the refractive index of the optical fiber with the desired character of the stick chromatic dispersion, and allows you to vary the chromatic dispersion in the desired range, at the same time, maintaining almost constant optical properties in two segments of fiber.

In addition, by making the optical fiber so that the above-mentioned optical properties reach maximum values within a deviation of ±10% of base radius, it is possible to maintain the slope of the dispersion curve is less than 0.05 PS/(nm2·km), which makes it possible to provide a single-mode optical fiber that is designed for use in high-speed communication system.

In addition, since the change of the radius of the core does not lead to a significant change in the effective cross section of the core Andeffthis method allows to suppress nonlinear effects in single-mode optical fiber.

For explaining the second example of a single-mode optical fiber contact figa-7.

The profile of the refractive index single-mode optical fiber used in this example shown in figure 1.

When designing single-mode optical fiber used radii of the core and the relative refractive index difference between, are presented in Table 3, and the calculated values of the optical properties of single-mode optical fibers are presented in Table 4.

Table 3

r2/r1r3/r1Δ1Δ2Δ3
2,03,00,50-0,200,20

Table 4

Wavelength cutoff [nm]Aeff[µm2]PDM[µm]Chromatic dispersion [PS/(nm· km)]The slope of the dispersion curve [PS/nm2·km)]Losses at bends [dB/m]
142049,33to 7.93+6,8+0,0293,2

Note: the values evaluated at the wavelength of 1550 nm; losses at bends ⊘ 20.

On figa-5D shows the changes in optical properties by changing the core radius of the optical fiber, the profile of the refractive index of which is presented in figure 1 and in Table 3, and figa shows the change of the chromatic dispersion at the wavelength of 1550 nm; figv shows the change in the slope of the dispersion curve at the wavelength of 1550 nm; figs shows the change in the effective cross section of the core Andeffat the wavelength of 1550 nm; and fig.5D shows the variation in losses at bends in the curve diameter ⊘ 20. The radius of the core, pending what about the x-axis, is the relative value, expressed in percentage from baseline mean radius, in this example, the base radius of the core r3is 10.25 μm.

From figa-5D follows that, unlike chromatic dispersion and losses in the bends, which vary monotonically with changing radius, the effective cross-section of the core Andeffand the slope of the dispersion curve reaches the corresponding limit values within a deviation of ±5% from the base radius of the core.

In the first example, Andeffand the slope of the dispersion curve reach maximum values at about the same radius of the core, but, to obtain the objectives of the present invention, the radii of the core, the corresponding limit values, do not necessarily coincide, so that, as in this example, sufficient to limit values were in the range of the radius of the core, amounting to ±5% of base radius of the core, and, in this example, by adjusting the radius of the core within ±5%, you can modify the chromatic dispersion in the range of +4~+10 PS/(nm· km), the same time, maintaining effective cross section of the core Andeffand the slope of the dispersion curve is almost constant.

The core material made in accordance with the structural parameters presented in figure 1 and in Table 3, usage is arranged in the manufacture of test specimens of the optical fiber, the radii of the core which was varied in the range of about ±5% relative to the base radius of the core, in order to evaluate their optical properties. On figa shows the change in the effective cross section of the core Andeffand figv shows the change in the slope of the dispersion curve. In both cases, the abscissa axis is delayed chromatic dispersion at the wavelength of 1550 nm. On figa, 6V bold dots And indicate the measured values for the obtained optical fiber, and the solid lines indicate calculated values. According figa, 6B, the effective cross-section of the core Andeffand the slope of the dispersion curve dependent chromatic dispersion. From figa, 6V, it follows that the calculated values essentially agree with the measured values, and, consequently, it is possible to make optical fibers having different values of the chromatic dispersion, but are practically the same effective cross-section of the core Andeffand the slope of the dispersion curve in two segments of fiber.

7 shows the characteristics of chromatic dispersion in optical fibers a and b, presented on figa, 6V. Chromatic dispersion of both the optical fibers a and b is greater than 2 PS/(nm· km) in S-band, C-band and L-band, indicating their suitability for use in the MDR system.

If we compare these results with those obtained in the first example, the optical fiber, shown in figure 4, which shows similar properties in the S-, and L-band, you can see that the chromatic dispersion of the optical fiber, shown in figure 4, more than 10 PS/ (nm· km) at a wavelength of 1625 nm, while the optical fiber shown in Fig.7, is able to keep it below 7 PS/(nm· km), which leads to the advantage that the optical fiber from the point of view of the accumulated dispersion.

In addition, although the chromatic dispersion of the optical fiber at a wavelength of 1625 nm, shown in Fig.7, is approximately the same as the optical fiber As shown in figure 4, it allows to obtain the value of chromatic dispersion at a wavelength of 1460 nm, greater than As shown in figure 4, which determines its effectiveness in suppressing the effects of four wave mixing in the S-range.

Accordingly, a single-mode optical fiber, considered in this example, consisting of a core and a shell, the core of which consists of at least two layers with different refractive indexes can be obtained by making such optical fiber, in which at least two optical properties (for example, the effective cross-section of the core Andeffand the slope of the dispersion curve) reaches the corresponding limit values when changing the radius Serdtsev who are within certain limits relative to the base radius, that allows you to implement a single-mode optical fiber on the basis of a single profile of the refractive index of the optical fiber, and enables you to vary the chromatic dispersion in the desired range and to have the desired characteristics of the chromatic dispersion at the same time, maintaining almost constant optical properties in two segments of fiber.

In addition, by making the optical fiber so that the above-mentioned optical properties reach maximum values within a deviation of ±5% of base radius, it is possible to maintain the slope of the dispersion curve is less than 0.03 PS/(nm2·km), which makes it possible to provide a single-mode optical fiber that is designed for use in high-speed communication system.

In addition, since the change of the radius of the core does not lead to a significant change in the effective cross section of the core Andeffthis method allows to suppress nonlinear effects in single-mode optical fiber.

For explaining the third example of a single-mode optical fiber contact figa-10.

In this example, is made of single-mode optical fiber, to which at least two optical properties reach the relevant limit values in the field values of the chromatic dispersion covering p is positive and negative values.

The profile of the refractive index single-mode optical fiber used in this example shown in figure 1.

When designing single-mode optical fiber used radii of the core and the relative refractive index difference between, are presented in Table 5, and the calculated values of the optical properties of single-mode optical fibers are presented in Table 6.

Table 5

r2/r1r3/r1Δ1Δ2Δ3
2,03,00,65-0,250,25

Table 6

Wavelength cutoff [nm]Andeff[µm2]PDM [µm]Chromatic dispersion [PS/(nm· km)]The slope of the dispersion curve [PS/nm2·km)]Losses at bends [dB/m]
145037,966,97+1,68+0,0190,1

Note: the values evaluated at the wavelength of 1550 nm; losses at bends ⊘ 20.

On figa-80D shows how to change the optical properties (characteristics) with the change of the radius of the fibre the optical fibre, the profile of the refractive index of which is presented in figure 1 and in Table 5, and figa shows the change of the chromatic dispersion at the wavelength of 1550 nm; figv shows the change in the slope of the dispersion curve at the wavelength of 1550 nm; figs shows the change in the effective cross section of the core Andeffat the wavelength of 1550 nm; and fig.8D shows the variation in losses at bends in the curve diameter ⊘ 20. The radius of the core, pending on the x-axis is the relative value, expressed in percentage from baseline mean radius, in this example, the base radius of the core r3equal cent to 8.85 μm.

In the region of wavelengths shown in figa-8D, the chromatic dispersion can be varied within ±10 PS/(nm· km), providing a changing radius of the core within ±5% with respect to the core radius, allowing you to get virtually zero chromatic dispersion. On the other hand, Aeffand the slope of the dispersion curve reaches in this area limits and remain almost constant.

The core material made in accordance with the structural parameters presented in figure 1 and in Table 5, was used in the manufacture of test specimens of the optical fiber, the core radii are varied in the range of about ±5% relative to the base is the range of the core, in order to evaluate their optical properties. On figa shows the change in the effective cross section of the core Andeffand figv shows the change in the slope of the dispersion curve. In both cases, the abscissa axis is delayed chromatic dispersion at the wavelength of 1550 nm. On figa, 9V, bold dots And indicate the measured values for the obtained optical fiber, and the solid lines indicate calculated values. From figa, 9V, it follows that the calculated values essentially agree with the measured values.

Thus, it was confirmed that at the wavelength of 1550 nm, while the optical fiber And has a chromatic dispersion -8 PS/(nm· km), which is very different from the chromatic dispersion of +8 PS/(nm· km) of optical fiber, it is possible to make optical fibers having almost the same Aseffand the slope of the dispersion curve.

Accordingly, a single-mode optical fiber, considered in this example, can be obtained by manufacturing an optical fiber, in which at least two optical properties (for example, the effective cross-section of the core Andeffand the slope of the dispersion curve) reaches the corresponding limit values when changing the radius of the core, in which the chromatic dispersion changes from a positive to a negative value is I, that allows you to implement a single-mode optical fiber on the basis of uniform distribution profile of the refractive index of the optical fiber, which has a positive or negative chromatic dispersion at the same time, maintaining almost constant optical properties in two segments of fiber.

In addition, by making the optical fiber so that the above-mentioned optical properties reach maximum values within a deviation of ±5% of base radius, it is possible to maintain the slope of the dispersion curve is less than 0.03 PS/(nm2·km), which makes it possible to provide a single-mode optical fiber that is designed for use in high-speed communication system.

For explaining the fourth example of the single-mode optical fiber contact figa-14.

The main difference between single-mode optical fiber, considered in this example, is to improve the dispersion characteristics described in the third example. For optical fibers, are considered in the third example, is characterized by the conversion of the sign of the chromatic dispersion at almost constant Andeffand the slope of the dispersion curve, but in this example, changing the sign of both the variances and the slope of the dispersion curve of the optical fiber, and Aeffremains unchanged.

The profile of the refractive index single-mode optical fiber used in this example shown in figure 1.

When designing single-mode optical fiber used radii of the core and the relative refractive index difference between, are presented in Table 7, and the calculated values of the optical properties of single-mode optical fibers are presented in Table 8.

Table 7

r2/r1r3/r1Δ1Δ2Δ3
2,53,00,70-0,300,60

Table 8

Wavelength cutoff [nm]Andeff[µm2]PDM [µm]Chromatic dispersion [PS/(nm· km)]The slope of the dispersion curve [PS/nm2·km)]Losses at bends [dB/m]
144032,236,41+1,54+0,0010,17

Note: the values evaluated at the wavelength of 1550 nm; losses at bends ⊘ 20.

On figa-11D shows the changes in optical properties by changing the core radius of the optical in the window, the profile of the refractive index of which is presented in figure 1 and in Table 7, and figa shows the change of the chromatic dispersion at the wavelength of 1550 nm; figv shows the change in the slope of the dispersion curve at the wavelength of 1550 nm; figs shows the change in the effective cross section of the core Andeffat the wavelength of 1550 nm; and fig.11D shows the variation in losses at bends in the curve diameter ⊘ 20. The radius of the core, pending on the x-axis is the relative value, expressed in percentage from baseline mean radius, in this example, the base radius of the core n38.3 microns.

In this example, Aeffalso reaches its maximum value when changing the radius of the core, but the nature of the change of the slope of the dispersion curve of the optical fiber is different from the one considered in the examples from the first to the third, in which the slope of the dispersion curve reaches the limit value, but varies in a small range. This example differs from the previous examples that the slope of the dispersion curve varies within very wide limits, as shown on FIGU, resulting in a change of sign of the value.

The core material made in accordance with the structural parameters presented in figure 1 and in Table 7, used to manufacturer the test samples of the optical fiber, the radii of the core which was varied in the range of about ±10% relative to the base radius of the core, to evaluate their optical properties. On figa shows the change in the effective cross section of the core Andeffand figv shows the change in the slope of the dispersion curve. In both cases, the abscissa axis is delayed chromatic dispersion at the wavelength of 1550 nm. On figa, 12V bold dots And indicate the measured values for the obtained optical fiber, and the solid lines indicate calculated values. From figa, 12V follows that settlement

values essentially agree with the measured values.

In addition, figs shows the dependence of DME (relative slope of the dispersion curve) from chromatic dispersion, and DME is a parameter defined by the following expression:

DME = the slope of the dispersion curve/chromatic dispersion, measured in nm-1.

This example demonstrates the possibility of making an optical fiber, which has Aeffand DME are almost constant, and the chromatic dispersion of which differs in sign but equal in absolute value.

Optical fiber and optical fiber provided on figs have approximately the same values DME, and values of the chromatic dispersion, the same is about the absolute value, but opposite in sign. Therefore, the slope of the dispersion curve can be compensated using a combination of such optical fibers.

On Fig shows the chromatic dispersion of optical fibers And, In presented at figa-12C, and the chromatic dispersion of the compound optic line obtained by joining the optical fiber And the optical fiber Century This composite optical communication line is the ratio of the lengths of 1:1 for two types of optical fibers.

From Fig follows that the composite optical link allows you to adjust the absolute value of the chromatic dispersion, reducing it to less than 2 PS/(nm· km) in all ranges of S, C and L. in Other words, the use of optical fiber, the profile of the refractive index of which is illustrated in this example, it enables to make imocompendium optical fiber, is able to adjust its own dispersion characteristics only by changing the radius of the core.

Accordingly, a single-mode optical fiber, considered in this example, can be obtained by making such optical fiber, in which optical properties (features) (e.g., the effective cross-section of the core Andeffand the slope of the dispersion curve) reach maximum values when measuring the drop radius of the core, when the slope of the dispersion curve changes sign, resulting in two segments of fiber chromatic dispersion and dispersion slope of the curve can have opposite signs, while the optical properties remain practically constant.

In addition, self-compensated optical communication line, which adjusts the slope of the dispersion curve, provided by the Association of such single-mode fibers with the formation of a composite optical communication lines.

It should be noted that although, in this example, as the parameter reaches the limit value, choose the effective cross section of the core Andeffthe same effects can be obtained by selecting the diameter of the field of fashion as a parameter reaches the limit value.

1. Single-mode optical fiber containing a core and a shell, and the core contains two or more layers having different refractive indices, and at least one optical characteristic reaches extreme values in a given range of the radius of the core when changing the radius of the core, while the optical characteristic is at least the slope of the dispersion curve, the effective core area or the diameter of the field of fashion, and the wavelength cutoff, which is equal to 1450 nm or less.

2. Single-mode optical fiber is according to claim 1, characterized in that the optical characteristic reaches extreme values within a deviation of ±10% from the base radius of the core.

3. Single-mode optical fiber according to claim 2, characterized in that the optical characteristic reaches extreme values within a deviation of ±5% from the base radius of the core.

4. Single-mode optical fiber according to claim 1, characterized in that at least one optical characteristic depends on the chromatic dispersion, reaching extreme values.

5. Single-mode optical fiber according to claim 4, characterized in that the optical characteristic reaches extreme values in the field, covering positive and negative values of the chromatic dispersion.

6. Single-mode optical fiber according to claim 1, wherein the optical characteristic is the slope of the dispersion curve.

7. Single-mode optical fiber according to claim 5, characterized in that the optical characteristic reaches extreme values in the field, covering positive and negative values of the slope of the dispersion curve.

8. Single-mode optical fiber according to claim 1, wherein the optical characteristic is an effective cross section of the core or the diameter of the field of fashion.

9. Single-mode optical fiber is according to claim 6, characterized in that the slope of the dispersion curve is not more than 0.05 PS/(nm2·km) in the working wavelength range.

10. Single-mode optical fiber according to claim 1, characterized in that the slope of the dispersion curve is not more than 0,03 PS/(nm2·km) in the working wavelength range.

11. Single-mode optical fiber according to claim 1, characterized in that at least one of the layers with different refractive indices that make up the core has a refractive index less than the refractive index of the shell.

12. Composite optics that compensate for the slope of the dispersion curve by combining single-mode optical fiber according to claim 7.



 

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