JP2006514316A - Chromatic dispersion compensating optical fiber - Google Patents

Abstract

The present invention continuously extends from the center toward the periphery, with a central section having a maximum refractive index larger than the refractive index of the cladding, an embedded section having a minimum refractive index smaller than the refractive index of the cladding, and a refractive index of the cladding. Including an annular section having a maximum refractive index that is large and smaller than the maximum refractive index of the central section, and a clad having a constant refractive index, and when the wavelength is 1550 nm, the chromatic dispersion is less than −8 ps / nm · km, Multiband chromatic dispersion compensation light having an absolute value of the ratio of dispersion to chromatic dispersion gradient of greater than 750 nm, a mode diameter of greater than 5 μm, and a bending loss of less than 400 dB / m for a radius of 10 mm when the wavelength is 1625 nm Related to fiber.

Description

  The present invention relates to the field of optical fibers for wavelength division multiplexing transmission networks.

  Increasing the information transmission speed in this type of network requires compensation for chromatic dispersion and chromatic dispersion slope over an increasingly wider spectral band. The so-called S band corresponds to a spectral band with wavelengths ranging from about 1460 nm to 1530 nm. The so-called C band corresponds to a spectral band with wavelengths ranging from about 1530 nm to 1565 nm. The so-called L band corresponds to a spectral band with wavelengths ranging from about 1565 nm to 1625 nm. The so-called U band corresponds to a spectral band with wavelengths ranging from about 1625 nm to 1675 nm. The most commonly used spectral band is the C band. In addition to the C band, the tendency to use the S band, the L band, and even the U band is gradually appearing.

  In the prior art, several types of dispersion-shifted optical fibers (NZ-DSF: “non-zero dispersion shuffled fiber”) that reduce crosses nonlinear effects are used in dispersion-compensating fibers (DCF: “dispersion compensating fiber”). ), Which results in a transmission line with zero dispersion over a wide spectral range.

  For example, according to the first prior art described in WO 01/01179, it is known to use a chromatic dispersion compensating optical fiber having a small gradient. However, since the ratio of the chromatic dispersion to the chromatic dispersion gradient for this optical fiber is too small, it is not possible to effectively compensate for an NZDSF type line fiber having a small chromatic dispersion gradient.

  The second conventional technique introduced in the report entitled “dispersion flattened fiber high negative dispersion” at the meeting OECC / IOOC'01 is a chromatic dispersion compensating optical fiber having a very large ratio of chromatic dispersion to chromatic dispersion gradient. However, this was not confirmed in the simulation presented orally at this conference, and on the contrary, a normal value of a mode diameter of about 4 μm was presented.

  The present invention can compensate a NZ-DSF type line optical fiber having a small chromatic dispersion gradient, and has a sufficiently large ratio of chromatic dispersion to chromatic dispersion gradient and advantageously has a small chromatic dispersion gradient. Propose fiber. The chromatic dispersion compensating optical fiber according to the present invention can also be used in an optical transmission line having a very high bit rate, for example, exceeding 40 gigabits per second because the mode diameter is sufficiently large. The compromise realized with the chromatic dispersion compensating optical fiber according to the present invention allows for effective compensation over a very wide spectral range spanning the S-band, C-band, L-band, and U-band.

  According to the present invention, a chromatic dispersion compensating optical fiber in a plurality of spectral bands including at least a C band is provided for a wavelength division multiplexing transmission network, and a core having a variable refractive index distribution is continuously provided from the center toward the periphery. And a cladding having a constant refractive index, and the variable refractive index distribution of the core continuously from the center toward the periphery, the central section of the maximum refractive index larger than the refractive index of the cladding, and the refractive index of the cladding Including an embedded section with a small minimum refractive index and an annular section with a maximum refractive index that is greater than the refractive index of the cladding and less than the maximum refractive index of the central section, the radius and refractive index of each section being When the chromatic dispersion compensating optical fiber has a wavelength of 1550 nm, the chromatic dispersion is less than −8 ps / nm · km, and the ratio of the chromatic dispersion to the chromatic dispersion gradient is Pair value is greater than 750 nm, as the mode diameter is larger than 5 [mu] m, also, when the wavelength 1625 nm, bending to the radius 10mm loss is determined to be less than 400 dB / m.

  Preferably, the radius and refractive index of each section are determined so that the absolute value of the ratio between the chromatic dispersion and the chromatic dispersion slope of the chromatic dispersion compensating optical fiber is greater than 1500 nm when the wavelength is 1550 nm.

  Preferably, the chromatic dispersion compensating optical fiber according to the present invention compensates the chromatic dispersion of the line optical fiber in the spectral bands S, C, L, and U.

Preferably, the radius and the refractive index of each section of the chromatic dispersion compensating optical fiber according to the present invention have an absolute value of less than 0.02 ps / nm ² · km when the chromatic dispersion compensating optical fiber has a wavelength of 1550 nm. It is determined to have a chromatic dispersion slope.

Preferably, the radius and the refractive index of each section of the chromatic dispersion compensating optical fiber according to the present invention are determined so that the chromatic dispersion compensating optical fiber has an effective area larger than 20 μm ² when the wavelength is 1550 nm.

  The chromatic dispersion compensating optical fiber according to the present invention is combined with the line optical fiber of the optical fiber transmission system. In an embodiment, an optical fiber transmission system includes a combination of a line optical fiber and an inline chromatic dispersion compensating optical fiber according to the present invention. In another embodiment, an optical fiber transmission system includes a combination of a line optical fiber and a module chromatic dispersion compensating optical fiber according to the present invention.

  In a first preferred embodiment of the present invention, a chromatic dispersion compensating optical fiber according to the present invention includes a first type variable index profile of a core having three sections. The variable refractive index profile of the first type of the core is continuously embedded from the center to the periphery, with the central section of the maximum refractive index larger than the refractive index of the cladding and the embedded with the minimum refractive index smaller than the refractive index of the cladding. It consists of a section and an annular section with a maximum refractive index that is greater than the refractive index of the cladding and less than the maximum refractive index of the central section. The central section is preferably trapezoidal or rectangular, but may be triangular or α-shaped, for example. The other sections are preferably rectangular, but these sections may also be trapezoidal, triangular, or α-shaped, for example.

  In order to widen the spectral range for compensating the chromatic dispersion of the line optical fiber as effectively as possible by the chromatic dispersion compensating optical fiber according to the present invention and to improve other characteristics of the chromatic dispersion compensating optical fiber according to the present invention, Some suitable ranges and relationships are listed below, particularly for the refractive index and radius of the refractive index profile of this type of core.

  In the first series of chromatic dispersion compensating optical fibers, when the radius and refractive index of each section are 1550 nm, the chromatic dispersion of the chromatic dispersion compensating optical fiber is −40 ps / nm · km to −8 ps / nm · km. To be determined. In the first series, it is particularly advantageous that the chromatic dispersion gradient of the chromatic dispersion compensating optical fiber according to the present invention is smaller than that in the second series described later.

Preferably, the difference (Δn ₂ ) between the lowest refractive index of the buried section and the refractive index of the cladding is −3.0 × 10 ⁻³ to 0.0 × 10 ⁻³ , The outer diameter (r ₂ ) is 5.8 μm to 8.5 μm.

Preferably, the difference (Δn ₃ ) between the maximum refractive index of the annular section and the refractive index of the cladding is 1.0 × 10 ⁻³ to 6.0 × 10 ⁻³ , and the outer diameter (r _{3 of the} annular section) ) Is 7.2 μm to 9.7 μm.

が、３９×１０^−３μｍ^２から６５×１０^−３μｍ^２である。 Preferably, between the radius zero and the radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the cladding, twice the integral of the product of the refractive index difference and the radius for the cladding.

Is 39 × 10 ⁻³ μm ² to 65 × 10 ⁻³ μm ² .

が、−１５０×１０^−３μｍ^２から−１０×１０^−３μｍ^２である。 Preferably, between the radius (r ₁ ) of the central section having a refractive index greater than that of the cladding and the radius (r ₂ ) of the embedded section having a refractive index smaller than that of the cladding. Is twice the integral of the product of the refractive index difference and the radius of the cladding.

Is −150 × 10 ⁻³ μm ² to −10 × 10 ⁻³ μm ² .

が、３０×１０^−３μｍ^２から１４０×１０^−３μｍ^２である。 Preferably, between the radius of the embedded section portion (r ₂ ) having a refractive index less than that of the cladding and the radius of the annular section portion (r ₃ ) having a refractive index greater than that of the cladding. Is twice the integral of the product of the refractive index difference and the radius of the cladding.

Is from 30 × 10 ⁻³ μm ² to 140 × 10 ⁻³ μm ² .

が、５９×１０^−３μｍ^３から１２３×１０^−３μｍ^３である。 Preferably, the integral of the product of the difference in refractive index with respect to the refractive index of the cladding and the square of the radius between the radius of zero and the radius (r ₁ ) of the central section having a refractive index greater than that of the cladding. 3 times the value

Is from 59 × 10 ⁻³ μm ³ to 123 × 10 ⁻³ μm ³ .

When the central section is rectangular, the difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is preferably 14.0 × 10 ⁻³ to 20.0 × 10 ⁻³ The radius (r ₁ ) of the central section having a refractive index greater than the refractive index is preferably 1.4 μm to 1.9 μm.

When the central section is trapezoidal, the difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is preferably 14.0 × 10 ⁻³ to 20.0 × 10 ⁻³ The radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the central section is preferably 1.4 μm to 1.9 μm, and the radius (r _1a ) of the central section having the maximum refractive index of the central section. However, it is preferably 1.3 μm to 1.9 μm.

  In the second series of chromatic dispersion compensating optical fibers, the radius and refractive index of each section are determined so that the chromatic dispersion of the chromatic dispersion compensating optical fiber is less than −40 ps / nm · km when the wavelength is 1550 nm. .

Preferably, the difference (Δn ₂ ) between the minimum refractive index of the embedded section and the refractive index of the cladding is from −5.0 × 10 ⁻³ to 0.0 × 10 ⁻³ , and is outside the embedded section. The diameter (r ₂ ) is 3.7 μm to 6.7 μm.

Preferably, the difference (Δn ₃ ) between the maximum refractive index of the annular section and the refractive index of the cladding is 1.0 × 10 ⁻³ to 8.0 × 10 ⁻³ , and the outer diameter (r ₃ ) of the annular section Is 6.1 μm to 8.4 μm.

が、３２×１０^−３μｍ^２から５２×１０^−３μｍ^２である。 Preferably, between the radius zero and the radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the cladding, twice the integral of the product of the refractive index difference and the radius for the cladding.

Is 32 × 10 ⁻³ μm ² to 52 × 10 ⁻³ μm ² .

が、−７０×１０^−３μｍ^２から−４×１０^−３μｍ^２である。 Preferably, between the radius (r ₁ ) of the central section having a refractive index greater than that of the cladding and the radius (r ₂ ) of the embedded section having a refractive index smaller than that of the cladding. Is twice the integral of the product of the refractive index difference and the radius of the cladding.

Is −70 × 10 ⁻³ μm ² to −4 × 10 ⁻³ μm ² .

が、７×１０^−３μｍ^２から１５０×１０^−３μｍ^２である。 Preferably, between the radius of the embedded section portion (r ₂ ) having a refractive index less than that of the cladding and the radius of the annular section portion (r ₃ ) having a refractive index greater than that of the cladding. Is twice the integral of the product of the refractive index difference and the radius of the cladding.

Is from 7 × 10 ⁻³ μm ² to 150 × 10 ⁻³ μm ² .

が、４０×１０^−３μｍ^３から８０×１０^−３μｍ^３である。 Preferably, the integral of the product of the difference in refractive index with respect to the refractive index of the cladding and the square of the radius between the radius of zero and the radius (r ₁ ) of the central section having a refractive index greater than that of the cladding. 3 times the value

Is 40 × 10 ⁻³ μm ³ to 80 × 10 ⁻³ μm ³ .

When the central section is rectangular, the difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is preferably 17.0 × 10 ⁻³ to 25.0 × 10 ⁻³ The radius (r ₁ ) of the central section having a refractive index greater than the refractive index is preferably 1.2 μm to 1.7 μm.

When the central section is trapezoidal, the difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is preferably 17.0 × 10 ⁻³ to 25.0 × 10 ⁻³ The radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the central section is preferably 1.2 μm to 1.7 μm, and the radius (r _1a ) of the central section having the maximum refractive index of the central section. However, it is preferably 1.1 μm to 1.7 μm.

  Preferably, for all chromatic dispersion compensating optical fibers according to the present invention corresponding to the first embodiment, the radius and refractive index of each section are such that the chromatic dispersion compensating optical fiber has a theoretical cutoff greater than 1600 nm. Determined to have a wavelength.

  In a second preferred embodiment of the present invention, a chromatic dispersion compensating optical fiber according to the present invention includes a second type variable refractive index profile of a core having four sections. The variable refractive index profile of the second type of core is continuous from the center to the periphery, with the central section of the maximum refractive index larger than the refractive index of the cladding, and the first refractive index of the minimum refractive index smaller than the refractive index of the cladding. An embedded section, an annular section having a maximum refractive index that is greater than the refractive index of the cladding and less than the maximum refractive index of the central section, and a second embedded section having a minimum refractive index that is less than the refractive index of the cladding. Composed. The central section is preferably rectangular, but may be trapezoidal, triangular or α-shaped. The other sections are preferably rectangular, but may be trapezoidal, triangular, or α-shaped, for example.

  In the third embodiment, the chromatic dispersion compensating optical fiber according to the present invention has a variable refractive index distribution of the third type core, and the variable refractive index distribution of the third type core extends from the center toward the periphery. In succession, the central section of the maximum refractive index larger than the refractive index of the cladding, the embedded section of the minimum refractive index smaller than the refractive index of the cladding, and the maximum refractive index of the central section larger than the refractive index of the cladding. A first annular section having a smaller maximum refractive index and a second annular section having a maximum refractive index greater than the refractive index of the cladding and greater than the refractive index of the first annular section. The central section is preferably rectangular, but may be trapezoidal, triangular or α-shaped. The other sections are preferably rectangular, but may be trapezoidal, triangular, or α-shaped, for example.

  In the fourth embodiment, the chromatic dispersion compensating optical fiber according to the present invention includes the variable refractive index profile of the fourth type core, and the variable refractive index profile of the fourth type core is from the center toward the periphery. Successively, a central section of maximum refractive index greater than the refractive index of the cladding, a first embedded section of minimum refractive index less than the refractive index of the cladding, and a first embedded smaller than the refractive index of the cladding and A second embedded section having a minimum refractive index that is greater than the refractive index of the section, and an annular section having a maximum refractive index that is greater than the refractive index of the cladding and less than the maximum refractive index of the center section. The central section is preferably rectangular, but may be trapezoidal, triangular or α-shaped. The other sections are preferably rectangular, but may be trapezoidal, triangular, or α-shaped, for example.

  Preferably, for all chromatic dispersion compensating optical fibers according to the present invention corresponding to the second, third, and fourth embodiments, the radius and refractive index of each section are such that the chromatic dispersion compensating optical fiber is 1550 nm or more. Determined to have a large theoretical cutoff wavelength.

  The invention will be better understood and other features and advantages will become apparent from the following description and accompanying drawings, given by way of example.

  FIG. 1 schematically shows an example of a refractive index profile of the first type having three sections of a chromatic dispersion compensating optical fiber according to the present invention. In the first section called the central section, the maximum refractive index difference from the constant cladding refractive index is Δn1, and the outer diameter r1. The maximum refractive index difference Δn1 is positive. Preferably, the refractive index is constant and maximum between the radius zero and the radius r1. In the second section called the embedded section, the maximum refractive index difference from the constant cladding refractive index is Δn2, and the outer diameter r2. The maximum refractive index difference Δn2 is negative. Preferably, the refractive index is constant between the radius r1 and the radius r2. In the third section called the annular section, the maximum refractive index difference from the constant cladding refractive index is Δn3, and the outer diameter is r3. The maximum refractive index difference Δn3 is positive. Preferably, the refractive index is constant between the radius r2 and the radius r3. When the radius r3 is exceeded, the refractive index of the cladding becomes constant.

  FIG. 2 is a table containing radius values and index difference values for ten example index profile examples of this first type of implementation of a chromatic dispersion compensating optical fiber according to the present invention. The left column is numbered from 1a to 10a in this example. The next three columns represent the radius of the variable refractive index profile of the core in units of μm. The last three columns represent the refractive index difference of 1000 times (no unit).

FIG. 3 is a table including some characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The left column is numbered from 1a to 10a in the examples. For each example considered, the other columns show the properties of the optical fiber corresponding to that example. The next column shows the chromatic dispersion slope C ′ (unit: ps / nm ² · km) at a wavelength of 1550 nm. The next column represents the ratio (unit: nm) between chromatic dispersion C and chromatic dispersion gradient C ′ at a wavelength of 1550 nm. The next column shows the mode diameter 2W ₀₂ (unit: μm) at a wavelength of 1550 nm. The last column shows the theoretical cutoff wavelength λ _cth (unit: nm).

FIG. 4 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The left column contains an example that has already been numbered as described above. For each example considered, the other columns show the properties of the optical fiber corresponding to that example. The next four columns show the effective area S _eff (unit: μm ² ) at wavelengths of 1460 nm, 1550 nm, 1625 nm, and 1675 nm, respectively.

  FIG. 5 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The left column contains an example that has already been numbered as described above. For each example considered, the other columns show the properties of the optical fiber corresponding to that example. The next four columns show chromatic dispersion C (unit: ps / nm · km) at wavelengths of 1460 nm, 1550 nm, 1625 nm, and 1675 nm, respectively.

  FIG. 6 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The left column contains an example that has already been numbered as described above. For each example considered, the other columns show the properties of the optical fiber corresponding to that example. The next three columns show the maximum bending loss threshold (in dB / m) for a radius of 10 mm at wavelengths of 1550 nm, 1625 nm, and 1675 nm, respectively. For example, for Example 1a, the bending loss is less than 3 dB / m. The next three columns show the maximum bending loss threshold (in dB / m) for a radius of 30 mm at wavelengths of 1550 nm, 1625 nm, and 1675 nm, respectively.

  FIG. 7 schematically shows another example of the first type of refractive index profile having three sections of a chromatic dispersion compensating optical fiber according to the present invention. In the first section called the central section, the maximum refractive index difference with respect to a constant refractive index of the cladding is Δn1, and the outer diameter is r1b. The maximum refractive index difference Δn1 is positive. Preferably, the refractive index is constant and maximum between the radius zero and the radius r1a, and is equal to the refractive index of the cladding when the radius value is r1, and when the radius value is r1b, Refractive index is reached. In the second section, also referred to as an embedded section, the maximum refractive index difference from the constant refractive index of the cladding is Δn2, and the outer diameter is r2. The maximum refractive index difference Δn2 is negative. Preferably, the refractive index is constant between the radius r1b and the radius r2. In a third section, also called an annular section, the maximum refractive index difference from the constant refractive index of the cladding is Δn3, and the outer diameter is r3. The maximum refractive index difference Δn3 is positive. Preferably, the refractive index is constant between the radius r2 and the radius r3. When the radius r3 is exceeded, the refractive index of the cladding becomes constant.

  FIG. 8 shows a table containing radius values and refractive index difference values for ten examples of refractive index profiles of another example of this first type of chromatic dispersion compensating optical fiber according to the present invention. . The left column is a number assigned to this example from 1b to 10b. The next five columns represent the radius of the variable refractive index profile of the core in units of μm. The last three columns show 1000 times the refractive index difference (no unit).

  FIG. 9 is a table including some characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. This description is the same as FIG.

  FIG. 10 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The description is the same as FIG.

  FIG. 11 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The description is the same as FIG.

  FIG. 12 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The description is the same as FIG.

  FIG. 13 schematically shows refractive index distributions of the second, third, and fourth types having four sections of the chromatic dispersion compensating optical fiber according to the present invention. In the first section called the central section, the maximum refractive index difference from the constant cladding refractive index is Δn1, and the outer diameter r1. The maximum refractive index difference Δn1 is positive. Preferably, the refractive index is constant between the radius zero and the radius r1. In the second section called the embedded section, the maximum refractive index difference from the constant cladding refractive index is Δn2, and the outer diameter r2. The maximum refractive index difference Δn2 is negative. Preferably, the refractive index is constant between the radius r1 and the radius r2. For the second and third types of refractive index profiles, the third section, called the annular section, has a maximum refractive index difference Δn3 with a constant cladding refractive index and an outer diameter of r3. . The maximum refractive index difference Δn3 is positive. Preferably, the refractive index is constant between the radius r2 and the radius r3. For the fourth type of refractive index profile, the third section, called the embedded section, has a maximum refractive index difference Δn3 with a constant cladding refractive index and an outer diameter r3. The maximum refractive index difference Δn3 is negative. Preferably, the refractive index is constant between the radius r2 and the radius r3. For the second type of refractive index profile, the fourth section, called the embedded section, has a maximum refractive index difference of Δn4 from the constant refractive index of the cladding and an outer diameter of r4. The maximum refractive index difference Δn4 is negative. Preferably, the refractive index is constant between the radius r3 and the radius r4. When the radius r4 is exceeded, the refractive index of the cladding becomes constant. For the third and fourth types of refractive index distributions, the fourth section, called the annular section, has a maximum refractive index difference of Δn4 from the constant cladding refractive index and an outer diameter of r4. The maximum refractive index difference Δn4 is positive. Preferably, the refractive index is constant between the radius r3 and the radius r4. When the radius r4 is exceeded, the refractive index of the cladding becomes constant.

  FIG. 14 is a table including radius values and refractive index difference values for ten examples of the second, third, and fourth type refractive index profiles of the chromatic dispersion compensating optical fiber according to the present invention. is there. The left column is numbered from 1c to 10c in this example. The next four columns represent the radius of the core variable refractive index profile in units of μm. The last four columns represent 1000 times the refractive index difference (no unit).

  FIG. 15 is a table including some characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The description is the same as in FIG.

  FIG. 16 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The description is the same as FIG.

  FIG. 17 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The description is the same as in FIG.

  FIG. 18 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. The description is the same as in FIG.

  FIG. 19 shows S, C, L, U of examples of the refractive index distributions 8a, 8b, and 2c, with the chromatic dispersion C (unit: ps / nm · km) on the ordinate and the wavelength λ (unit: nm) on the abscissa. The change in chromatic dispersion in the band is indicated by curves A, A ′, and A ″, respectively.

According to a first preferred additional embodiment of the present invention, in the chromatic dispersion compensating optical fiber according to the present invention, the radius and refractive index of each section are also the wavelength when the chromatic dispersion compensating optical fiber has a wavelength of 1550 nm. The dispersion is −200 ps / nm · km to −40 ps / nm · km, and the difference Δn ₁ between the maximum refractive index in the central section and the refractive index of the cladding is 17.0 × 10 ⁻³ to 25.0 × 10 ^{− 3} and is determined to be. By setting the interval of the values taken by the difference between the maximum refractive index of the central section and the refractive index of the cladding as a moderation, the difference between the maximum refractive index of the central section and the refractive index of the cladding is about 30 × 10 ^−3. The optical fiber has better attenuation and / or better bending loss than the above optical fiber, and at the same time, the difference between the maximum refractive index of the central section and the refractive index of the cladding is more negative than the optical fiber of about 12 × 10 ⁻³ or less. A chromatic dispersion compensating optical fiber having a chromatic dispersion of

が、−７０×１０^−３μｍ^２から−４×１０^−３μｍ^２になるように同様に決定される。中央区間の最大屈折率とクラッドの屈折率との差がとる値の間隔を中庸にすることによって、中央区間の最大屈折率とクラッドの屈折率との差が約３０×１０^−３以上である光ファイバよりも優れた減衰および／または優れた曲げ損失を有すると同時に、中央区間の最大屈折率とクラッドの屈折率との差が約１２×１０^−３以下である光ファイバよりも負になる波長分散を有する、波長分散補償光ファイバが得られる。 According to a second preferred additional embodiment of the present invention, in the chromatic dispersion compensating optical fiber according to the present invention, the radius and refractive index of each section are also the wavelength when the chromatic dispersion compensating optical fiber has a wavelength of 1550 nm. The dispersion is less than −40 ps / nm · km, and the difference Δn ₁ between the maximum refractive index of the central section and the refractive index of the cladding is 17.0 × 10 ⁻³ to 25.0 × 10 ⁻³ , Refractive index for the cladding between the radius (r ₁ ) of the central section having a refractive index greater than the refractive index and the radius (r ₂ ) of the embedded section having a refractive index less than the refractive index of the cladding. Double the integral of the product of difference and radius

Is determined in the same manner so as to be −70 × 10 ⁻³ μm ² to −4 × 10 ⁻³ μm ² . The difference between the maximum refractive index of the central section and the refractive index of the cladding is about 30 × 10 ⁻³ or more by setting the interval of the values taken by the difference between the maximum refractive index of the central section and the refractive index of the cladding as a middle. It has better attenuation and / or better bending loss than optical fibers, while being more negative than optical fibers where the difference between the maximum refractive index of the central section and the refractive index of the cladding is about 12 × 10 ⁻³ or less A chromatic dispersion compensating optical fiber having chromatic dispersion is obtained.

  The first and second preferred additional embodiments of the present invention involve an optical fiber for a module.

  According to a third preferred additional embodiment of the present invention, in the chromatic dispersion compensating optical fiber according to the present invention, the radius and refractive index of each section are also the wavelength when the chromatic dispersion compensating optical fiber has a wavelength of 1550 nm. The dispersion is determined to be −40 ps / nm · km to −15 ps / nm · km, and the chromatic dispersion slope is negative. A chromatic dispersion compensating optical fiber having an average absolute value of chromatic dispersion is more advantageous than a chromatic dispersion compensating optical fiber having a small absolute value of chromatic dispersion. This is because when the same line optical fiber is compensated, the length can be short. Since the attenuation of the chromatic dispersion compensating optical fiber is generally larger than the attenuation of the line optical fiber, it is advantageous that the transmission line includes as little of the chromatic dispersion compensating optical fiber as possible and as much of the line optical fiber as possible. A chromatic dispersion compensating optical fiber having a negative chromatic dispersion slope is more advantageous than a chromatic dispersion compensating optical fiber having a positive chromatic dispersion slope. This is because the positive chromatic dispersion slope of most line optical fibers can be compensated in the same manner.

According to a third preferred additional embodiment of the present invention, in the chromatic dispersion compensating optical fiber according to the present invention, the radius and refractive index of each section are also centered when the chromatic dispersion compensating optical fiber has a wavelength of 1550 nm. The difference Δn ₁ between the maximum refractive index of the section and the refractive index of the cladding is determined to be 14.0 × 10 ⁻³ to 20.0 × 10 ⁻³ . The difference between the maximum refractive index of the central section and the refractive index of the cladding is about 30 × 10 ⁻³ or more by setting the interval of the values taken by the difference between the maximum refractive index of the central section and the refractive index of the cladding as a middle. It has better attenuation and / or better bending loss than optical fibers, while being more negative than optical fibers where the difference between the maximum refractive index of the central section and the refractive index of the cladding is about 12 × 10 ⁻³ or less A chromatic dispersion compensating optical fiber having chromatic dispersion is obtained.

  A third preferred additional embodiment of the present invention involves an in-line optical fiber.

It is a figure which shows roughly an example of the refractive index profile of the 1st type which has three areas of the wavelength dispersion compensation optical fiber by this invention. It is a table | surface which shows the value of a radius, and the value of a refractive index difference with respect to ten refractive index distribution examples of the example of the 1st type of the wavelength dispersion compensation optical fiber by this invention. 3 is a table including some characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. 3 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. 3 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. 3 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. It is a figure which shows schematically another example of the refractive index profile of the 1st type which has three areas of the wavelength dispersion compensation optical fiber by this invention. 7 is a table including radius values and refractive index difference values for ten refractive index profile examples of another embodiment of the first type of chromatic dispersion compensating optical fiber according to the present invention. 9 is a table including some characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. 9 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. 8. 9 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. 8. 9 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. 8. It is a figure which shows schematically the refractive index distribution of the 2nd, 3rd, and 4th type which has four areas of the wavelength dispersion compensation optical fiber by this invention. 6 is a table including radius values and refractive index difference values for ten examples of refractive index distributions of the second, third, and fourth types of chromatic dispersion compensating optical fibers according to the present invention. 15 is a table including some characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. 15 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. 15 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. 15 is a table including other characteristics of the refractive index distribution of the chromatic dispersion compensating optical fiber according to the present invention shown in FIG. It is a graph which shows the change of the chromatic dispersion in the S, C, L, U band of the example of refractive index distribution 8a, 8b, 2c.

Claims (39)

A chromatic dispersion compensating optical fiber in a plurality of spectral bands including at least the C band,
For wavelength division multiplexing transmission networks,
Including a core having a variable refractive index profile and then a clad having a constant refractive index, continuously from the center toward the periphery,
The variable refractive index profile of the core is continuous from the center to the periphery,
A central section of maximum refractive index greater than the refractive index of the cladding;
An embedded section with a minimum refractive index smaller than the refractive index of the cladding;
An annular section with a maximum refractive index that is greater than the refractive index of the cladding and less than the maximum refractive index of the central section;
The radius and refractive index of each section are as follows.
When the wavelength is 1550 nm,
The chromatic dispersion is less than −8 ps / nm · km,
The absolute value of the ratio of chromatic dispersion to chromatic dispersion slope is greater than 750 nm,
To make the mode diameter larger than 5 μm,
When the wavelength is 1625 nm,
A chromatic dispersion compensating optical fiber that is determined so that a bending loss with respect to a radius of 10 mm is less than 400 dB / m.   The radius and refractive index of each section are determined so that the absolute value of the ratio between the chromatic dispersion and the chromatic dispersion gradient of the chromatic dispersion compensating optical fiber is greater than 1500 nm when the wavelength is 1550 nm. The chromatic dispersion compensating optical fiber according to claim 1.   The chromatic dispersion compensating optical fiber according to claim 1 or 2, wherein the chromatic dispersion compensating optical fiber compensates the chromatic dispersion of the line optical fiber in the spectral bands S, C, L, and U. The variable refractive index profile of the core is continuous from the center to the periphery,
A central section of maximum refractive index greater than the refractive index of the cladding;
An embedded section with a minimum refractive index smaller than the refractive index of the cladding;
4. The chromatic dispersion compensating optical fiber according to claim 1, wherein the chromatic dispersion compensating optical fiber is configured by an annular section having a maximum refractive index that is larger than a refractive index of the cladding and smaller than a maximum refractive index of the central section.   The radius and refractive index of each section are determined so that the chromatic dispersion of the chromatic dispersion compensating optical fiber is −40 ps / nm · km to −8 ps / nm · km when the wavelength is 1550 nm. The chromatic dispersion compensating optical fiber according to claim 4. The difference (Δn ₂ ) between the lowest refractive index of the embedded section and the refractive index of the cladding is −3.0 × 10 ⁻³ to 0.0 × 10 ⁻³ ;
6. The chromatic dispersion compensating optical fiber according to claim 5, wherein an outer diameter (r ₂ ) of the embedded section is 5.8 μm to 8.5 μm. The difference (Δn ₃ ) between the maximum refractive index of the annular section and the refractive index of the cladding is 1.0 × 10 ⁻³ to 6.0 × 10 ⁻³ ,
7. The chromatic dispersion compensating optical fiber according to claim 5, wherein an outer diameter (r ₃ ) of the annular section is 7.2 μm to 9.7 μm. Between the radius zero and the radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the cladding, twice the integral of the product of the refractive index difference and the radius for the cladding

8 is 39 × 10 ⁻³ μm ² to 65 × 10 ⁻³ μm ^2. 8. The chromatic dispersion compensating optical fiber according to claim 5, wherein Between the radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the cladding and the radius (r ₂ ) of the embedded section having a refractive index smaller than the refractive index of the cladding. Double value of integral of product of refractive index difference and radius

The chromatic dispersion compensating optical fiber according to claim 5, wherein is from −150 × 10 ⁻³ μm ² to −10 × 10 ⁻³ μm ² . Between the radius of the embedded section portion (r ₂ ) having a refractive index less than the refractive index of the cladding and the radius (r ₃ ) of the annular section portion having a refractive index greater than the refractive index of the cladding. Double value of integral of product of refractive index difference and radius

The chromatic dispersion compensating optical fiber according to any one of claims 5 to 9, wherein is from 30 × 10 ⁻³ μm ² to 140 × 10 ⁻³ μm ² . Between the radius zero and the radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the cladding, the triple value of the integral of the product of the refractive index difference with respect to the cladding refractive index and the square of the radius

The chromatic dispersion compensating optical fiber according to any one of claims 5 to 10, wherein is from 59 × 10 ⁻³ μm ³ to 123 × 10 ⁻³ μm ³ .   The chromatic dispersion compensating optical fiber according to any one of claims 5 to 11, wherein the central section is rectangular. The difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is 14.0 × 10 ⁻³ to 20.0 × 10 ⁻³ ,
13. The chromatic dispersion compensating optical fiber according to claim 12, wherein the radius (r ₁ ) of the central section having a refractive index larger than that of the cladding is 1.4 μm to 1.9 μm.   The chromatic dispersion compensating optical fiber according to any one of claims 5 to 11, wherein the central section is trapezoidal. The difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is 14.0 × 10 ⁻³ to 20.0 × 10 ⁻³ ,
The radius (r ₁ ) of the central section having a refractive index greater than that of the cladding is 1.4 μm to 1.9 μm;
The chromatic dispersion compensating optical fiber according to claim 14, wherein the radius (r _1a ) of the central section portion having the maximum refractive index of the central section is 1.31 μm to 1.88 μm.   The radius and refractive index of each section are determined so that the chromatic dispersion of the chromatic dispersion compensating optical fiber is less than -40 ps / nm · km when the wavelength is 1550 nm. Chromatic dispersion compensating optical fiber. The difference (Δn ₂ ) between the minimum refractive index of the embedded section and the refractive index of the cladding is from −5.5 × 10 ⁻³ to 0.0 × 10 ⁻³ ;
17. The chromatic dispersion compensating optical fiber according to claim 16, wherein an outer diameter (r ₂ ) of the embedded section is 3.7 μm to 6.7 μm. The difference (Δn ₃ ) between the maximum refractive index of the annular section and the refractive index of the cladding is 1.0 × 10 ⁻³ to 8.0 × 10 ⁻³ ,
18. The chromatic dispersion compensating optical fiber according to claim 16, wherein an outer diameter (r ₃ ) of the annular section is 6.1 μm to 8.4 μm. Between the radius zero and the radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the cladding, twice the integral of the product of the refractive index difference and the radius for the cladding

The chromatic dispersion compensating optical fiber according to any one of claims 16 to 18, characterized in that is 32 × 10 ⁻³ μm ² to 52 × 10 ⁻³ μm ² . Between the radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the cladding and the radius (r ₂ ) of the embedded section having a refractive index smaller than the refractive index of the cladding. Double value of integral of product of refractive index difference and radius

The chromatic dispersion compensating optical fiber according to any one of claims 16 to 19, wherein the chromatic dispersion compensating optical fiber is from -70 x 10 ^-3 µm ² to -4 x 10 ^-3 µm ² . Between the radius of the embedded section portion (r ₂ ) having a refractive index less than the refractive index of the cladding and the radius (r ₃ ) of the annular section portion having a refractive index greater than the refractive index of the cladding. Double value of integral of product of refractive index difference and radius

21 is a wavelength dispersion compensating optical fiber according to any one of claims 16 to 20, characterized in that is 7 × 10 ⁻³ μm ² to 150 × 10 ⁻³ μm ² . Three times the integral of the product of the difference in refractive index for the refractive index of the cladding and the square of the radius between the radius zero and the radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the cladding.

The chromatic dispersion compensating optical fiber according to any one of claims 16 to 21, wherein is 40 × 10 ⁻³ μm ³ to 80 × 10 ⁻³ μm ³ .   The chromatic dispersion compensating optical fiber according to any one of claims 16 to 22, wherein the central section is rectangular. The difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is 17.0 × 10 ⁻³ to 25.0 × 10 ⁻³ ,
24. The chromatic dispersion compensating optical fiber according to claim 23, wherein the radius (r ₁ ) of the central section having a refractive index greater than that of the cladding is 1.2 μm to 1.7 μm.   The chromatic dispersion compensating optical fiber according to any one of claims 16 to 22, wherein the central section is trapezoidal. The difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is 17.0 × 10 ⁻³ to 25.0 × 10 ⁻³ ,
The radius (r ₁ ) of the central section having a refractive index greater than that of the cladding is 1.2 μm to 1.7 μm;
26. The chromatic dispersion compensating optical fiber according to claim 25, wherein the radius (r _1a ) of the central section portion having the maximum refractive index of the central section is 1.11 μm to 1.70 μm.   27. The radius and refractive index of each section are determined such that the chromatic dispersion compensating optical fiber has a theoretical cutoff wavelength greater than 1600 nm. Chromatic dispersion compensating optical fiber. The variable refractive index profile of the core is continuous from the center to the periphery,
A central section of maximum refractive index greater than the refractive index of the cladding;
An embedded section with a minimum refractive index smaller than the refractive index of the cladding;
A first annular section having a maximum refractive index that is greater than the refractive index of the cladding and less than the maximum refractive index of the central section;
4. The second annular section having a maximum refractive index that is greater than the refractive index of the cladding and greater than the refractive index of the first annular section. The chromatic dispersion compensating optical fiber described. The variable refractive index profile of the core is continuous from the center to the periphery,
A central section of maximum refractive index greater than the refractive index of the cladding;
A first embedded section with a minimum refractive index less than the refractive index of the cladding;
A second embedded section having a minimum refractive index that is less than the refractive index of the cladding and greater than the refractive index of the first embedded section;
The chromatic dispersion compensation according to any one of claims 1 to 3, wherein the chromatic dispersion compensation includes an annular section having a maximum refractive index that is larger than a refractive index of the clad and smaller than a maximum refractive index of the central section. Optical fiber. The variable refractive index profile of the core is continuous from the center to the periphery,
A central section of maximum refractive index greater than the refractive index of the cladding;
A first embedded section with a minimum refractive index less than the refractive index of the cladding;
An annular section with a maximum refractive index that is greater than the refractive index of the cladding and less than the maximum refractive index of the central section;
4. The chromatic dispersion compensating optical fiber according to claim 1, comprising: a second embedded section having a minimum refractive index smaller than a refractive index of the cladding. 5.   31. The radius and refractive index of each section are determined so that the chromatic dispersion compensating optical fiber has a theoretical cutoff wavelength greater than 1550 nm. Chromatic dispersion compensating optical fiber. The radius and the refractive index of each section are determined such that the chromatic dispersion compensating optical fiber has a chromatic dispersion slope whose absolute value is smaller than 0.02 ps / nm ² · km when the wavelength is 1550 nm. The chromatic dispersion compensating optical fiber according to any one of claims 1 to 31. The radius and refractive index of each section are determined so that the chromatic dispersion compensating optical fiber has an effective area larger than 20 μm ^{2 at} a wavelength of 1550 nm. The chromatic dispersion compensating optical fiber described in the paragraph. The radius and refractive index of each section are as follows when the chromatic dispersion compensating optical fiber has a wavelength of 1550 nm:
The chromatic dispersion is -200 ps / nm · km to -40 ps / nm · km,
The difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is determined to be 17.0 × 10 ⁻³ to 25.0 × 10 ^−3. The chromatic dispersion compensating optical fiber according to any one of 1 to 33. The radius and refractive index of each section are as follows when the chromatic dispersion compensating optical fiber has a wavelength of 1550 nm:
The chromatic dispersion is less than −40 ps / nm · km,
The difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is 17.0 × 10 ⁻³ to 25.0 × 10 ⁻³ ,
Between the radius (r ₁ ) of the central section having a refractive index greater than the refractive index of the cladding and the radius (r ₂ ) of the embedded section having a refractive index smaller than the refractive index of the cladding. Double value of integral of product of refractive index difference and radius

35. The chromatic dispersion compensating optical fiber according to any one of claims 1 to 34, characterized in that is determined to be −70 × 10 ⁻³ μm ² to −4 × 10 ⁻³ μm ^2. . The radius and refractive index of each section are as follows when the chromatic dispersion compensating optical fiber has a wavelength of 1550 nm:
The chromatic dispersion is −40 ps / nm · km to −15 ps / nm · km,
36. The chromatic dispersion compensating optical fiber according to claim 1, wherein the chromatic dispersion compensating optical fiber is determined so as to have a negative chromatic dispersion slope. The wavelength according to claim 36, characterized in that the difference (Δn ₁ ) between the maximum refractive index of the central section and the refractive index of the cladding is 14.0 x 10 ^-3 to 20.0 x 10 ^-3. Dispersion compensating optical fiber.   An optical fiber transmission system comprising a combination of a line optical fiber and the chromatic dispersion compensating optical fiber according to any one of claims 1 to 37 when the chromatic dispersion compensating optical fiber is in-line.   An optical fiber transmission system comprising a combination of a line optical fiber and the chromatic dispersion compensating optical fiber according to any one of claims 1 to 37 when the chromatic dispersion compensating optical fiber is a module.

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