JP2001337245A - Dispersion compensation optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersion compensation optical fiber of a dispersion slope compensation type which is capable of realizing low loss and low nonlinerity while maintaining the intrinsic function of compensating wavelength dispersion and dispersion slope. SOLUTION: The dispersion compensation optical fiber which is <=4.0 in the absolute value of the wavelength dispersion over the entire part of a transmission path connected to an optical fiber for transmission having an effective sectional area of >=30 μm2, bending loss of <=40 dB/m and wavelength dispersion of -40 to -10 ps/nm/km in the use wavelength band selected from 1.53 to 1.62 μm and having the position wavelength dispersion, is <=0.03 ps/nm2/km in the absolute value of the dispersion slope and has a substantially single mode propagatable cut-off wavelength at the use length used for the transmission path described above is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention occurs when an optical signal in the 1.53 to 1.62 .mu.m band is transmitted using a transmission optical fiber having a zero dispersion wavelength on the shorter wavelength side than 1.53 .mu.m. The present invention relates to a dispersion compensation optical fiber of a dispersion slope compensation type for simultaneously compensating for chromatic dispersion and dispersion slope, and in particular, to reduce nonlinear effects.

[0002]

2. Description of the Related Art In a recent optical communication system in which a wavelength band selected from 1.53 to 1.62 μm is used, a communication speed, a transmission distance, and a capacity are rapidly increased. I'm advancing. As a technique for increasing the distance, an ultra-long-distance non-regenerative relay that amplifies an optical signal at predetermined intervals using an erbium-doped optical fiber amplifier has already been commercialized. As a technique for increasing the capacity, wavelength division multiplexing transmission is cited. In order to further increase the capacity, the number of multiplexed wavelengths is increased, and development is proceeding in the direction of expanding the wavelength band.

In such a system, a transmission optical fiber is required to have the following characteristics, for example.
In increasing the communication speed, it has a small chromatic dispersion,
Preferably, the chromatic dispersion is not zero. This is because when the chromatic dispersion is zero, four-photon mixing, which is one of the non-linear effects, is likely to occur, and the transmission characteristics deteriorate. In multi-wavelength transmission, it is also important that the dispersion slope is small. The dispersion slope is the slope of the graph when the wavelength is plotted on the horizontal axis and the wavelength dispersion is plotted on the vertical axis. When the dispersion slope is small, the dispersion of the transmission state between the optical signals of the wavelengths to be multiplexed becomes small, and deterioration of the transmission characteristics can be prevented. In extending the distance, it is also important that non-linear effects hardly occur. This is because transmission characteristics are degraded when a nonlinear effect occurs, but especially when an erbium optical amplifier is used as described above, the nonlinear effect is likely to occur due to a sharp increase in the intensity of an optical signal due to amplification. Further, in the wavelength multiplex transmission, since the power of an optical signal to be transmitted is large in the first place, there is a problem that the transmission deterioration due to the non-linear effect is likely to increase due to the amplification of the erbium optical amplifier.

The magnitude of the non-linear effect is represented by n ₂ / Aeff. Here, n ₂ is the nonlinear refractive index of the optical fiber, and Aeff is the effective area of the optical fiber. To reduce the non-linear effect, reduce n ₂ or Aef
Although it is necessary to increase f, it is difficult to greatly reduce it with a silica-based optical fiber because n ₂ is a value specific to the material. For this reason, the current development of nonlinear suppression optical fibers focuses on increasing the effective area.

In a system using a wavelength band of 1.53 to 1.62 μm, a dispersion-shifted optical fiber designed to have a chromatic dispersion of 1.55 μm near zero is preferable from the viewpoint of chromatic dispersion. However, the conventional dispersion-shifted optical fiber has a problem that if the dispersion slope is reduced, a large effective area cannot be realized.

[0006] Therefore, it has already been constructed all over the world.
Attempts have been made to transmit an optical signal in this working wavelength band using a 3 μm band single mode optical fiber network. The effective area of the 1.3 μm single mode optical fiber in this used wave band is relatively large, so that the nonlinear effect can be suppressed. When an optical signal in this operating wavelength band is transmitted using a single mode optical fiber for 1.3 μm, about +
Since chromatic dispersion of 17 ps / nm / km occurs and transmission characteristics are greatly deteriorated, a system combining a dispersion compensating optical fiber has been proposed and commercialized. Since the dispersion compensating optical fiber has negative chromatic dispersion in this used wavelength band, the chromatic dispersion of the 1.3 μm single mode optical fiber can be offset. As a result, deterioration of the transmission characteristics of the entire system can be prevented, and high-speed communication can be achieved.

In this operating wavelength band, 1.3 μm
Since the single-mode optical fiber for m has a positive dispersion slope, a system has been proposed in which a dispersion compensating optical fiber having a negative dispersion slope compensates the dispersion slope together with the chromatic dispersion. As a dispersion slope compensation type dispersion compensating optical fiber, one having a W-type refractive index distribution exemplified in FIG. 2 has been developed. This refractive index distribution is composed of a core 11 and a clad 12 provided on the outer periphery thereof. The core 11 has a central core portion 13 having a refractive index higher than that of the center clad 12 and a core provided on the outer periphery thereof. And an intermediate core portion 14 having a lower refractive index than the clad 12.

Then, the intermediate core 1 with respect to the clad 12
And 2 of the specific refractive difference delta _12, the outer diameter 2 of the center relative refractive index difference delta ₁₁ of the core unit 11 and the central core portion 13, the cladding 12
By adjusting the ratio between a ₂ and the outer diameter 2b ₂ of the intermediate core portion 14, a characteristic capable of simultaneously compensating for the positive chromatic dispersion and the positive dispersion slope of the 1.3 μm single mode optical fiber can be obtained.

Further, from the viewpoint of improving bending loss and dispersion slope characteristics, the segmented W shown in FIG.
Dispersion compensating optical fiber of the dispersion slope compensation type having a refractive index distribution of the type has also been developed. This refractive index distribution is composed of a core 1 and a clad 2 provided on the outer periphery thereof,
The core 1 has a central core portion 3 having a higher refractive index than the center clad 2, an intermediate core portion 4 provided on the outer periphery thereof having a lower refractive index than the clad 2, and And a ring core portion 5 having a higher refractive index than the cladding 2.

Also in this case, the relative refractive index difference Δ ₁ of the central core portion 3 with respect to the cladding 2, the intermediate core portion 4 with respect to the cladding 2
Relative refractive index difference Δ ₂ , ring core portion 5 with respect to clad 2
Relative refractive index difference Δ ₃ , the ratio of the outer diameter b ₁ of the intermediate core portion 4 to the outer diameter a ₁ of the central core portion 3, and the central core portion 3
It has been reported that by adjusting the ratio of the outer diameter c ₁ of the ring core portion 5 to the outer diameter a ₁ of the optical fiber, characteristics that can simultaneously compensate the chromatic dispersion and the dispersion slope of the single-mode optical fiber for 1.3 μm can be obtained. .

Conventionally, these dispersion-slope compensation type dispersion compensating optical fibers are conventionally housed in, for example, an appropriate housing and incorporated in an optical communication system as a module. However, recently, studies have been made to convert the dispersion compensating optical fiber itself into a cable and insert it into a transmission line, and some reports have been made. If the dispersion compensating optical fiber itself can be used as the transmission line, the space for installing the module can be omitted, and the length of the optical fiber through which the optical signal is transmitted can be substantially shortened. This is because it can be improved.

[0012]

However, although a dispersion-slope-compensating type dispersion-compensating optical fiber which focuses on compensation of chromatic dispersion and dispersion slope and reduction of loss has been reported, it has been reported that the effective area is increased. Has not been effectively reviewed or reported. As described above, suppression of nonlinear effects is indispensable for high speed, long distance, and wavelength multiplexing, and when a dispersion compensation optical fiber of dispersion slope compensation type is inserted as a transmission line, the nonlinear Practical application may be difficult unless the effective cross-sectional area is such that the effect can be effectively suppressed.

Therefore, in the present invention, while maintaining the original functions of compensating for chromatic dispersion and dispersion slope,
An object of the present invention is to provide a dispersion compensation optical fiber of a dispersion slope compensation type capable of realizing low loss and low nonlinearity. Specifically, it is an object of the present invention to provide a dispersion compensating optical fiber having a large effective area for realizing low nonlinearity.

[0014]

In order to solve the above-mentioned problems, a dispersion compensating optical fiber according to the present invention has a diameter of 1.53 μm or less.
In the used wavelength band selected from 1.62 μm, the effective area is 30 μm ² or more, the bending loss is 40 dB / m or less,
The chromatic dispersion is -40 to -10 ps / nm / km, and the absolute value of the chromatic dispersion of the entire transmission line connected to the transmission optical fiber having positive chromatic dispersion is 4.0 ps / nm / km or less. The absolute value of the slope is 0.03 ps / nm ² / k
m or less, and has a cut-off wavelength capable of substantially single-mode propagation in a use length used for the transmission line. The dispersion compensating optical fiber includes a core and a clad formed on the outer periphery thereof, wherein the core is provided on the outer periphery of the central core portion having a higher refractive index than the clad. An intermediate core portion having a lower refractive index than the cladding, and a ring core portion provided on the outer periphery of the intermediate core portion and having a higher refractive index than the cladding, wherein the cladding is made of pure quartz. It is preferable to have a refractive index equal to or less than the value of the refractive index. When the outer diameter of the center core portion is 2a ₁ , the outer diameter of the ring core portion is 2b ₁ , and the outer diameter of the ring core portion is 2c ₁ , 2.0 ≦ b ₁ / a ₁ ≦ 3.0, 2.5 ≦ c ₁ / a ₁ ≦
4.0 a and, relative refractive index difference delta ₁ of the center core part and the cladding is from 0.6 to 0.9%, the relative refractive index difference delta ₂ of the intermediate core portion -0.30～-0.50 with respect to the cladding %, the relative refractive index difference delta ₃ ring core portion relative to the cladding 0.4
It is preferably 0.9%.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the used wavelength band is
A region having a predetermined wavelength width is selected from 1.53 μm to 1.62 μm according to the application. For example, 1.53 to 1.57
μm, 1.57 to 1.62 μm, or 1.53 to 1.
For example, the entire length is 62 μm. The effective area is

[0016]

(Equation 1)

## EQU1 ## The larger the effective area is, the lower the nonlinearity becomes, which is preferable. In the present invention, a wavelength of 30 μm ² or more, preferably 35 μm ² or more is obtained in the above-mentioned used wavelength band. The upper limit of the effective cross-sectional area is not particularly limited, but it can be manufactured as long as it is substantially in the range of 40 μm ² or less. When the thickness is less than 30 μm ^{2, the} effect of suppressing the nonlinear effect is reduced, which is inconvenient.

In the present invention, the bending loss is a bending diameter of 20.
mm. The bending loss is preferably as small as possible. In the present invention, in the use wavelength band, 4
0 dB / m or less, preferably 30 dB / m or less, substantially in the range of 0.1 to 10 dB / m is obtained. 4
If it exceeds 0 dB / m, it is inconvenient because the loss increases due to slight bending applied at the time of laying.

The chromatic dispersion of the dispersion compensating optical fiber of the present invention in the wavelength band used is -40 to -10 ps / nm /.
km, preferably -18 to -25 ps / nm / km. When it is larger than −10 ps / nm / km and approaches zero, it becomes difficult to compensate for the positive chromatic dispersion of the optical fiber for transmission. If it is smaller than -40 ps / nm / km, the value of Aeff becomes smaller,
It is practically difficult to manufacture.

Further, the dispersion compensating optical fiber of the present invention, when connected to a transmission optical fiber having a positive chromatic dispersion and a positive dispersion slope with a predetermined use length to form a transmission line, The absolute value of the chromatic dispersion of the entire path is 4.0 ps /
The chromatic dispersion of the optical fiber for transmission can be compensated so as to be not more than nm / km, preferably not more than 2.0 ps / nm / km, and at the same time, the absolute value of the dispersion slope of the entire transmission line is 0.03 ps. / Nm ² / km or less, preferably 0.01 ps / nm ² / km or less, the dispersion slope of the transmission optical fiber is designed to be compensated.

A typical example of the transmission optical fiber to be compensated is a single mode optical fiber for 1.3 μm. For example, the zero dispersion is set to a wavelength shorter than 1.53 μm which is the lower limit of the wavelength band used in the present invention. Any material having a wavelength can be used without particular limitation. The used length of the dispersion compensating optical fiber is set according to the characteristics of the transmission optical fiber to be compensated as described above. In the present invention, since the dispersion compensating optical fiber itself has a low loss and a low non-linear characteristic that can be used as a transmission line, even a relatively long use length causes deterioration of the transmission loss of the entire transmission line. Nothing. Although not particularly limited, the used length of the dispersion compensating optical fiber is set to be 1.0 to 2.5 times the transmission optical fiber.

The optimum dispersion slope of the dispersion compensating optical fiber varies depending on the dispersion slope and the length of the transmission optical fiber to be compensated, and is not particularly limited. 0.12 ps / nm ²
/ Km or so.

Further, since the dispersion compensating optical fiber of the present invention compensates for a single mode optical fiber, it is preferable that the cutoff wavelength has a value which guarantees single mode propagation in the above-mentioned use length. As the cutoff wavelength, a value measured by the CCITT 2m method is usually used. In an actual long use state, single mode propagation can be performed even if the cutoff wavelength in the 2m method is longer than the use wavelength. . Therefore, the cutoff wavelength is a value that substantially guarantees single mode propagation in an actual use state in consideration of the use length.

In order to obtain these characteristics, the first condition is that the dispersion compensating optical fiber of the present invention has a segmented W-type refractive index distribution exemplified in FIG. That is, this refractive index distribution shape includes the core 1 and the clad 2 formed on the outer periphery thereof. The core 1 is provided with a central core portion 3 having a higher refractive index than the clad 2 and an intermediate core portion 4 provided on the outer periphery of the central core portion 3 and having a lower refractive index than the clad 2. And a ring core portion 5 provided on the outer periphery of the intermediate core portion 4 and having a higher refractive index than the cladding 2.

In this refractive index distribution, for example, the core 1
The ring core 5 is made of germanium-added quartz glass, the intermediate core 4 is made of fluorine-added quartz glass, and the clad 2 is made of pure quartz glass or fluorine-added quartz glass. The cladding 2 preferably has a refractive index equal to or less than the refractive index of pure silica glass. The reason is that, by reducing the difference in softening temperature between the core 1 and the clad 2, the stress remaining in the central core portion 3 or the like after drawing can be reduced, and a low-loss optical fiber can be obtained.

In this refractive index distribution, assuming that the outer diameter of the central core is 2a ₁ , the outer diameter of the ring core is 2b ₁ , and the outer diameter of the ring core is 2c ₁ , 2.0 ≦ b ₁ / a ₁ ≦ 3.
0, 2.5 ≦ c ₁ / a ₁ ≦ 4.0, and the relative refractive index difference Δ ₁ of the center core portion 3 with respect to the cladding 2 is 0.6 to 0.9.
%, The relative refractive index difference Δ ₂ of the intermediate core portion 4 with respect to the cladding ₂
Is preferably -0.30 to -0.50%, and the relative refractive index difference [Delta] ₃ of the ring core 5 with respect to the cladding 2 is preferably 0.4 to 0.9%.

If b ₁ / a ₁ is less than 2.0, the effect of the intermediate core portion 4 is reduced, and Aeff is reduced. If b ₁ / a ₁ is more than 3.0, the bending loss increases, and the device cannot be used. c ₁
If / a ₁ is less than 2.5, the effect of the ring core portion 5 is reduced, and Aeff is reduced. If it exceeds 4.0, the bending loss is reduced and the device cannot be used. . Also, the relative refractive index difference delta ₁ bending loss increases is less than 0.6%, 0.9
If it exceeds%, Aeff becomes small. Moreover, (the closer to the refractive index of the clad 2) relative refractive index difference delta ₂ becomes large when than -0.30% Aeff becomes small, -0.5
If it is less than 0%, the bending loss becomes large, and it cannot be used. Also, the relative refractive index difference delta ₃ decreases the effect of the ring core portion 5 is less than 0.4% Aeff becomes small, the bending loss increases and exceeds 0.9%, can not be used.

In the dispersion compensating optical fiber of the present invention,
It has a segmented W-type refractive index distribution shown in FIG. 1,
Even if each structural parameter satisfies the above numerical range, a dispersion compensating optical fiber having the above characteristics is not always obtained. That is, b ₁ /
From five numerical ranges of a ₁ , c ₁ / a ₁ , Δ ₁ , Δ ₂ , and Δ ₃ ,
The dispersion compensating optical fiber of the present invention can be obtained only by selecting appropriate values by performing trial and error so as to realize the above-described characteristics. Therefore, in the dispersion compensating optical fiber of the present invention, it is difficult to specify simply by the numerical value range related to the structural parameter, so that the invention is specified by the characteristic value. Needless to say, such characteristics have not been obtained with the conventional dispersion compensating optical fiber.

The dispersion compensating optical fiber of the present invention is, for example,
Combination of ordinary VAD method and OVD method, MCVD
It can be manufactured by a method, a PCVD method, or the like.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments.

COMPARATIVE EXAMPLE A first material made of GeO ₂ -doped quartz glass was formed by a known method such as a VAD method or an MCVD method.
A columnar porous body including a layer and a second layer made of SiO ₂ provided on the outer periphery thereof was produced. The ratio of the second layer diameter / the first layer diameter was 4.0. The porous body is dehydrated with He and a chlorine-based gas in an atmosphere of about 1000 ° C., and then 5 L / min of SiF ₄ 1 L /
A rod was manufactured by simultaneously performing fluorine addition and transparent vitrification in an atmosphere of min. The rod is stretched to form a core base material, a porous body made of SiO ₂ for cladding is externally mounted around the core base material, dehydrated with He and a chlorine-based gas in an atmosphere of about 1000 ° C. To produce a glass preform. Then, a dispersion-compensating optical fiber having a W-type refractive index distribution shown in FIG. 1 was produced by drawing. Table 1 shows the optical characteristics of the dispersion compensating optical fiber at a used wavelength of 1.55 μm. The MFD in Table 1 is the mode field diameter, and the wavelength is the measurement wavelength (used wavelength) of the optical characteristics.

[0032]

[Table 1]

The dispersion compensation ratio in Table 1 is 1.3 μm
Dispersion slope per unit length of glue mode optical fiber
Per unit length of dispersion compensating fiber for absolute value of
Shows the ratio of the absolute value of the dispersion slope. In addition, one
1.5 of a general 1.3 μm band single mode optical fiber
The chromatic dispersion at 5 μm is +17 ps / nm / km,
Dispersion slope is + 0.060ps / nm ^Two/ Km.

From Table 1, the chromatic dispersion of this dispersion compensating optical fiber is -16.2 ps / nm / km.
The used length of the dispersion compensating optical fiber capable of completely compensating the chromatic dispersion of the 1.3-μm km single-mode optical fiber to zero was 1.05 km. The dispersion slope of the dispersion compensating optical fiber is -0.057 ps / nm.
² / km, the dispersion slope of the dispersion compensating optical fiber having this working length (1.05 km) is -0.060 ps / n.
m ² , indicating that the dispersion slope of 1 km of the 1.3 μm single mode optical fiber can be completely compensated.

Then, the same use length ratio of 1.3 μm was used.
The single-mode optical fiber for m and the dispersion compensating optical fiber were connected to construct a transmission line having a total length of 45 km. A of the dispersion compensating optical fiber used in the latter half of this transmission line
Since eff is 25.1 μm ^2, which is small, the transmission characteristics are greatly deteriorated due to the non-linear effect, and it is difficult to increase the transmission capacity or lengthen the transmission distance to apply to long-distance large-capacity transmission. I understand.

Example A rod was manufactured in the same manner as in the comparative example except that the size of each layer was changed. Then, the rod is stretched, and a porous body made of GeO ₂ -added quartz glass and SiO ₂ for the ring core and cladding is externally attached around the rod.
The substrate was dehydrated with e and a chlorine-based gas, and vitrified in a He atmosphere to obtain a base material. Then, it was stretched to produce a dispersion compensating optical fiber having a segmented W-type refractive index distribution shown in FIG. Tables 2 and 3 show the structural parameters of the obtained dispersion compensating optical fiber and the optical characteristics at a used wavelength of 1.55 μm.

[0037]

[Table 2]

[0038]

[Table 3]

From the results shown in Tables 2 and 3, all of the dispersion compensating optical fibers of Nos. 2 to 6 according to the present invention compensate for the chromatic dispersion and dispersion slope of the standard 1.3 μm single mode optical fiber. It was something that could be done. In addition, the use length in Table 3 shows the use length of the dispersion compensating optical fiber that can completely compensate for zero wavelength dispersion of the 1.3-μm single-mode optical fiber for 1.3 km for convenience. The chromatic dispersion or dispersion slope of the entire transmission line is defined as the chromatic dispersion or dispersion per unit length when a 1.3 km single mode optical fiber of 1 km and the dispersion compensating optical fiber of the used length are connected. The slope was shown.

A transmission line having a total length of 45 km was constructed by connecting a single mode optical fiber for 1.3 μm and a dispersion compensating optical fiber at the same use length ratio. Aef of the dispersion compensating optical fiber used in the latter half of this transmission line
Since f is as large as 30 μm ² or more, it has been found that the deterioration of the transmission characteristics due to the non-linear effect is small, and the transmission capacity can be increased or the transmission distance can be extended to perform long-distance large-capacity transmission. In addition, the dispersion compensating optical fiber was capable of single mode propagation in the used length used for this transmission line.

[0041]

As described above, in the dispersion compensating optical fiber of the present invention, while maintaining the original functions of compensating for chromatic dispersion and dispersion slope, a dispersion slope compensating fiber capable of realizing low loss and low nonlinearity. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a segmented W-type refractive index distribution.

FIG. 2 is a schematic diagram showing an example of a W-type refractive index distribution.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Core, 2 ... Clad, 3 ... Center core part, 4 ... Intermediate core part, 5 ... Ring core part

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 26, 2001 (2001.4.2
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 3

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

[0014]

In order to solve the above-mentioned problems, a dispersion compensating optical fiber according to the present invention has a diameter of 1.53 μm or less.
In the used wavelength band selected from 1.62 μm, the effective area is 30 μm ² or more, the bending loss is 40 dB / m or less,
The chromatic dispersion is -40 to -10 ps / nm / km, and the absolute value of the chromatic dispersion of the entire transmission line connected to the transmission optical fiber having positive chromatic dispersion is 4.0 ps / nm / km or less. The absolute value of the slope is 0.03 ps / nm ² / k
m or less, and has a cut-off wavelength capable of substantially single-mode propagation in a use length used for the transmission line. The dispersion compensating optical fiber includes a core and a clad formed on the outer periphery thereof, wherein the core is provided on the outer periphery of the central core portion having a higher refractive index than the clad. An intermediate core portion having a lower refractive index than the cladding, and a ring core portion provided on the outer periphery of the intermediate core portion and having a higher refractive index than the cladding, wherein the cladding is made of pure quartz. It is preferable to have a refractive index equal to or less than the value of the refractive index. When the outer diameter of the central core is 2a ₁ , the outer diameter of the intermediate core is 2b ₁ , and the outer diameter of the ring core is 2c ₁ , 2.0 ≦ b ₁ / a ₁ ≦ 3.0, 2.. 5 ≦ c ₁ / a ₁ ≦
4.0 a and, relative refractive index difference delta ₁ of the center core part and the cladding is from 0.6 to 0.9%, the relative refractive index difference delta ₂ of the intermediate core portion -0.30～-0.50 with respect to the cladding %, the relative refractive index difference delta ₃ ring core portion relative to the cladding 0.4
It is preferably 0.9%.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

In this refractive index distribution, outside the central core portion
Diameter 2a₁,Middle2b outer diameter of core₁Of the ring core
2c outside diameter₁2.0 ≦ b₁/ A₁≦ 3.0,
2.5 ≦ c₁/ A₁≦ 4.0, for cladding 2
Relative refractive index difference Δ of central core 3 ₁0.6-0.9%
Relative refractive index difference Δ of the intermediate core portion 4 with respect to the lad 2_TwoBut-
0.30 to -0.50%, ring core for clad 2
The relative refractive index difference Δ of the part 5_ThreeIs preferably 0.4 to 0.9%.
Good.

Continued on the front page (72) Akira Wada, Inventor 1440, Misaki, Sakura-shi, Chiba F-term in Fujikura Sakura Office (reference) 2H050 AB04Y AB05X AB10X AC09 AC14 AC28 AC71 AC73 AC75 AC76 AD01

Claims (3)

[Claims] 1. In an operating wavelength band selected from 1.53 μm to 1.62 μm, an effective area is 30 μm ² or more and a bending loss is 40 dB / m.
Hereinafter, the chromatic dispersion is -40 to -10 ps / nm / km, and the absolute value of the chromatic dispersion of the entire transmission line connected to the transmission optical fiber having positive chromatic dispersion is 4.0 ps / nm / km.
Hereinafter, the absolute value of the dispersion slope is 0.03 ps / nm ² /
km, and a cut-off wavelength capable of substantially single-mode propagation in a use length used for the transmission line. 2. The dispersion-compensating optical fiber according to claim 1, comprising: a core; and a clad formed on an outer periphery of the core, wherein the core has a higher refractive index than the clad; An intermediate core portion provided on the outer periphery of the central core portion and having a lower refractive index than the clad, and a ring core portion provided on the outer periphery of the intermediate core portion and having a higher refractive index than the clad. Wherein the cladding has a refractive index equal to or less than the refractive index of pure quartz. 3. The dispersion compensating optical fiber according to claim 2, wherein the outer diameter of the central core is 2a ₁ and the outer diameter of the ring core is 2a.
b ₁ , when the outer diameter of the ring core is 2c ₁ , 2.0 ≦
b ₁ / a ₁ ≦ 3.0, 2.5 ≦ c ₁ / a ₁ ≦ 4.0, and the relative refractive index difference Δ ₁ of the central core portion with respect to the cladding is 0.6.
0.9%, relative refractive index of the intermediate core portion difference delta ₂ is -0.30～-0.50% with respect to the cladding, the relative refractive index difference delta ₃ ring core portion relative to the cladding is from 0.4 to 0.9% A dispersion compensating optical fiber, characterized in that: