JP2002062450A - Dispersion compensating optical fiber and optical transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersion compensating optical fiber and an optical transmission line which decrease the absolute values of the wavelength dispersion and dispersion slope of S band signal light and are suitable for Raman amplification. SOLUTION: The dispersion compensating optical fiber 21 has a wavelength dispersion DDCF of <=-30 ps/nm/km, a ratio (SDCF/DDCF) of the wavelength dispersion DDCF of -0.05 to +0.05/nm and dispersion slope SDCF, a polarization mode dispersion of <=0.3 ps/km1/2, and a transmission loss of <=1 dB/km, and an excessive loss of <=0.2 dB/km due to the OH group of the wavelength 1.4 μm band at a wavelength of 1500 nm. Further, this dispersion compensating optical fiber 21 has a cutoff wavelength of <=1.4 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission line suitable for transmitting signal light in a wavelength band of 1.5 .mu.m, and a dispersion compensating optical fiber suitably used as a part of the optical transmission line. It is.

[0002]

2. Description of the Related Art Wavelength division multiplexing (WDM)
The on-multiplexing optical transmission system is for optically transmitting multi-wavelength signal light using one optical transmission line, and can transmit a large amount of information. In the WDM optical transmission system, further increase in capacity is required, and C band (wavelength 1.55 μm band) and L band (wavelength 1.59 μm).
μm band) as well as the S band (wavelength 1.50 μm)
The use of signal light in the band is also being studied.

Meanwhile, an Er-doped fiber amplifier (EDFA) using an optical fiber in which an Er element is added to an optical waveguide region as an optical amplification medium.
lifier) can efficiently amplify the signal light of the C band or the L band. Therefore, the C-band or L-band signal light is transmitted to the EDFA provided in the repeater.
, Which enables optical transmission and long-distance transmission. On the other hand, E
DFA cannot optically amplify S-band signal light. On the other hand, the Raman amplifier supplies Raman amplification pump light of a wavelength appropriately selected according to the wavelength of the signal light to the optical transmission line, and Raman amplifies the signal light propagating through the optical transmission line. The wavelength of the signal light to be Raman-amplified is arbitrary. Therefore, it is conceivable that the signal light of the C band and the L band is optically amplified by the EDFA, and the signal light of the S band is optically amplified by the Raman amplifier.

In order to increase the capacity, the optical transmission line must be
It is desired that both the absolute value of the chromatic dispersion and the absolute value of the dispersion slope are small in the signal light wavelength band. However, it is difficult to configure an optical transmission line having small absolute values of chromatic dispersion and dispersion slope using only one kind of optical fiber. Therefore, in general, two or more types of optical fibers (transmission optical fibers and dispersion compensating optical fibers for compensating chromatic dispersion of the transmission optical fibers) having different wavelength dispersion characteristics from each other are connected, and the entirety is connected. An optical transmission line having small absolute values of chromatic dispersion and dispersion slope is formed.

[0005]

In order to Raman-amplify S-band signal light, the wavelength of the Raman amplification pump light is 1.4.
It is necessary to be in the μm band. However, the dispersion compensating optical fiber used for compensating the chromatic dispersion of the transmission optical fiber has an excess loss due to OH groups in a wavelength band of 1.4 μm. Accordingly, the Raman amplification pump light of the wavelength band of 1.4 μm, which can Raman-amplify the S-band signal light,
Suffers a large loss when propagating through the dispersion compensating optical fiber,
Efficiency in Raman amplification of signal light is low, and it is difficult to construct an optical transmission line having small absolute values of chromatic dispersion and dispersion slope while performing Raman amplification.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a dispersion compensation light suitable for reducing the absolute values of chromatic dispersion and dispersion slope of S-band signal light and performing Raman amplification. It is an object to provide a fiber and an optical transmission line.

[0007]

SUMMARY OF THE INVENTION A dispersion compensating optical fiber according to the present invention has a chromatic dispersion at a wavelength of 1500 nm.
30 ps / nm / km or less, and the ratio (S / D) of the chromatic dispersion D to the dispersion slope S is -0.08 / nm to +0.
05 / nm and the polarization mode dispersion is 0.3 ps / km
Less than ^1/2 , the transmission loss is less than 1 dB / km,
Excessive loss due to OH group in wavelength 1.4μm band is 0.2dB
/ Km or less. When this dispersion compensating optical fiber is used, the chromatic dispersion and dispersion slope of the transmission optical fiber are compensated in the S band, and the absolute value of the chromatic dispersion of the optical transmission line including the transmission optical fiber and the dispersion compensating optical fiber is reduced. , S-band signal light. When the Raman amplification pumping light (wavelength 1.4 μm band) is supplied to the dispersion compensating optical fiber, the Raman amplification pumping light propagates through the dispersion compensating optical fiber with low loss and propagates through the dispersion compensating optical fiber. The S-band signal light is Raman-amplified with high efficiency.

[0008] The dispersion compensating optical fiber according to the present invention is characterized in that the cutoff wavelength is 1.4 μm or less. In this case, the dispersion compensating optical fiber has a wavelength of the Raman amplification pump light that can pump the S-band signal light.
Single mode operation is performed even in the 4 μm band.

Further, the dispersion compensating optical fiber according to the present invention is characterized in that it is covered with a hermetic coat. In this case, H ₂ is applied to the dispersion compensating optical fiber.
Can be prevented, and an increase in loss of the dispersion compensating optical fiber can be suppressed.

The optical transmission line according to the present invention has a wavelength of 1500n.
The wavelength dispersion is +2 ps / nm / km to +8 ps at m
/ Nm / km and dispersion slope is 0.055 ps / n
a transmission optical fiber of m ² / km to 0.065 ps / nm ² / km, and a dispersion according to the present invention having a length connected to the transmission optical fiber and having a slope compensation ratio of 50% to 150%. And a compensating optical fiber. Alternatively, the optical transmission line according to the present invention has a wavelength of 1500 n.
m, the chromatic dispersion is −3 ps / nm / km to +2 ps
/ Nm / km and the dispersion slope is 0.085 ps / n
a transmission optical fiber having a m ² / km to 0.095 ps / nm ² / km, and a dispersion according to the present invention having a length connected to the transmission optical fiber and having a slope compensation ratio of 50% to 150%. And a compensating optical fiber. Alternatively, the optical transmission line according to the present invention has a wavelength of 1500 n.
m, the chromatic dispersion is -1 ps / nm / km to +5 ps
/ Nm / km and the dispersion slope is 0.040 ps / n
a transmission optical fiber of m ² / km to 0.050 ps / nm ² / km, and a dispersion according to the present invention having a length connected to the transmission optical fiber and having a slope compensation rate of 50% to 150%. And a compensating optical fiber. According to this optical transmission line, in the S band, the chromatic dispersion and dispersion slope of the transmission optical fiber are compensated by the dispersion compensating optical fiber, and the absolute value of the chromatic dispersion of the optical transmission line including the transmission optical fiber and the dispersion compensating optical fiber is obtained. The value is small, which is suitable for transmitting S-band signal light. Also, when pumping light for Raman amplification (wavelength 1.4 μm band) is supplied to such an optical transmission line, the loss in the pumping light band for Raman amplification of the dispersion compensating optical fiber is low, so that the optical transmission line is wide. The pumping light for Raman amplification propagates over the region, and the S-band signal light propagating in the optical transmission line is Raman-amplified with high efficiency.

Further, the optical transmission line according to the present invention comprises Raman amplification pumping light supply means for supplying Raman amplification pumping light for Raman amplification of signal light propagating through the optical transmission line to the optical transmission line. It is further characterized by being provided. In this case, the pumping light for Raman amplification (wavelength: 1.4 μm band) is supplied to the optical transmission line by the Raman amplification pumping light supply unit, and the S-band signal light propagating through the optical transmission line is Raman-amplified.

[0012]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a schematic configuration diagram of an optical transmission system 1 including a dispersion compensating optical fiber 21 and an optical transmission line according to the present embodiment. In this optical transmission system 1, a transmission optical fiber 30 is laid between a repeater 10 and a repeater 20, and a dispersion compensating optical fiber 21, an optical coupler 22,
A Raman amplification excitation light source 23 and an EDFA 24 are provided in the repeater 20. The transmission optical fiber 30 and the dispersion compensating optical fiber 21 constitute an optical transmission line according to the present embodiment. In this optical transmission system 1, the repeater 1
0 to the repeater 20, the signal light included in any of the S band, the C band, and the L band is transmitted to the transmission optical fiber 30.
Is transmitted via

The dispersion compensating optical fiber 21 compensates for the chromatic dispersion of the transmission optical fiber 30 and also compensates for the dispersion slope. The optical coupler 22 outputs the signal light arriving from the dispersion compensating optical fiber 21 to the EDFA 24, and outputs the Raman amplification pumping light arriving from the Raman amplification pumping light source 23 to the dispersion compensating optical fiber 21. The Raman amplification pumping light source 23 is a transmission optical fiber 3
0 and the wavelength (1.4 μm) at which the S-band signal light of the signal light propagating through the dispersion compensating optical fiber 21 can be Raman amplified.
m) Raman amplification pump light is output. EDFA24
Optically amplifies and outputs the signal light included in one of the C band and the L band among the signal lights arriving from the optical coupler 22, and outputs the S band signal light.

In the optical transmission system 1, any one of the S-band, C-band, and L-band signal lights output from the repeater 10 propagates through the transmission optical fiber 30 and reaches the repeater 20. C of the signal light reaching the repeater 20
The band or L band signal light propagates through the dispersion compensating optical fiber 21 in the repeater 20, passes through the optical coupler 22, and is optically amplified by the EDFA 24. When the S-band signal light of the signal light propagates through the transmission optical fiber 30 and the dispersion compensating optical fiber 21, the optical coupler 22
, And is Raman-amplified by the Raman amplification pump light propagating from the dispersion compensating optical fiber 21 to the transmission optical fiber 30, then passes through the optical coupler 22, and passes through the EDFA 24 without being optically amplified.

As described above, in this optical transmission system 1,
The C band or L band signal light is optically amplified by the EDFA 24, and the S band signal light is dispersed in the dispersion compensating optical fiber 2.
1 is Raman amplified. The chromatic dispersion and dispersion slope of the transmission optical fiber 30 are compensated by the dispersion compensating optical fiber 21. Therefore, the optical transmission system 1 can perform long-distance, large-capacity optical transmission using a wide signal light wavelength band including the S band, the C band, and the L band.

The transmission optical fiber 30 has, for example, a wavelength of 1.
Chromatic dispersion is positive at 500 nm and several ps / nm
/ Km, which has a chromatic dispersion of +2 ps / nm / at a wavelength of 1500 nm, for example.
km~ + 8ps / nm / a km, dispersion slope is 0.055ps / nm ² /km~0.065ps/nm ²
/ Km. Alternatively, for example, at a wavelength of 1500 nm, the chromatic dispersion is −3 ps / nm / km to +2 ps / nm /
km, and the dispersion slope is 0.085 ps / nm ² /
km to 0.095 ps / nm ² / km. Or,
For example, at a wavelength of 1500 nm, chromatic dispersion is -1 ps /
nm / km~ + 5ps / nm / a km, dispersion slope is 0.040ps / nm ² /km~0.050ps/
nm ² / km.

On the other hand, the dispersion compensating optical fiber 21 according to the present embodiment has a wavelength dispersion D _{DCF at} a wavelength of 1500 nm.
Is -30 ps / nm / km or less, and the chromatic dispersion D _DCF
And the ratio (S _DCF / D _DCF ) of the dispersion slope S _DCF to −0.
08 / nm to + 0.05 / nm, the polarization mode dispersion is 0.3 ps / km ^1/2 or less, and the transmission loss is 1 dB.
/ Km or less, and excess loss due to OH groups in the wavelength band of 1.4 μm is 0.2 dB / km or less. The dispersion compensation optical fiber 21 has a cutoff wavelength of 1.4 μm or less. Hereinafter, such a dispersion compensating optical fiber 2 will be described.
1 will be described in detail.

FIG. 2 shows a dispersion compensating optical fiber according to this embodiment.
FIG. 3 is a diagram for explaining a refractive index profile of an eva 21. This
Of the dispersion compensating optical fiber has an outer diameter a including the center of the optical axis.
And the maximum refractive index is n₁And the first core region
And surround the region and have an outer diameter b and a refractive index of n_TwoThe first
A two-core region and a refractive index n surrounding the second core region
_ThreeAnd a cladding region. High refractive index in each area
Small relation is n₁> N_Three> N _Two It is. In this figure,
The relative refractive index difference of the first core region with respect to the cladding region is Δn
₁And the relative refraction of the second core region with respect to the cladding region
The rate difference is Δn_TwoIt is represented by

The dispersion compensating optical fiber 21 is based on silica glass, and GeO ₂ is added to the first core region and F element is added to the second core region. An optical fiber preform for manufacturing the dispersion compensating optical fiber 21 is:
For the first core region, VAD (vapor-phase axial de
position) method and the rod-in collapse method and the VAD
It is manufactured by a method or an OVD (outside vapor deposition) method. Alternatively, an optical fiber preform for manufacturing the dispersion compensating optical fiber 21 is manufactured by an MCVD (modified chemical vapor deposition) method for the first core region, and manufactured by a VAD method for the second core region and the cladding region. Is done.

The OH group content in the first core region of the dispersion compensating optical fiber 21 can be reduced by performing a dehydration treatment when manufacturing the optical fiber preform, and the wavelength of the dispersion compensating optical fiber 21 is 1.4 μm. Excess loss due to OH groups in the band can be less than 0.2 dB / km. But,
When the OH group is removed, glass defects easily occur in the first core region of the dispersion compensating optical fiber 21, and the loss increases when the dispersion compensating optical fiber 21 is exposed to an H ₂ environment. Therefore, the dispersion-compensating optical fiber 21 according to the present embodiment is preferable that is coated with a hermetic coating, By doing so, H ₂ to the dispersion compensating optical fiber 21
Of the dispersion compensating optical fiber 21 can be prevented.
Can be suppressed from increasing. Thus, the S-band signal light is stably Raman-amplified in the dispersion compensating optical fiber 21.

It is preferable to perform the swing drawing in the drawing step of manufacturing the dispersion compensating optical fiber 21 by drawing the optical fiber preform. In this swing line drawing, the roller that passes through the drawn dispersion compensating optical fiber 21 until it reaches the winding bobbin is swung. Then, due to the swing, the anisotropic stress distribution in the dispersion compensating optical fiber 21 is reduced, and the polarization mode dispersion of the dispersion compensating optical fiber 21 is reduced to 0.1.
It is reduced to 3 ps / km ^1/2 or less.

FIGS. 3 to 8 are graphs showing the relationship between the chromatic dispersion at a wavelength of 1550 nm of the dispersion compensating optical fiber 21 according to the present embodiment and the slope compensation ratio.
Here, the slope compensation rate η of the dispersion compensating optical fiber 21
Is represented by the following equation: η = (D / S) / (D _DCF / S _DCF ). Here, _DCF is the chromatic dispersion of the dispersion compensating optical fiber 21, _SDCF is the dispersion slope of the dispersion compensating optical fiber 21, and D is the transmission optical fiber 30.
, And S is the dispersion slope of the transmission optical fiber 30. The chromatic dispersion D of the transmission optical fiber 30 at a wavelength of 1550 nm was +5 ps / nm / km, and the dispersion slope S was 0.06 ps / nm ² / km. In each of FIGS. 3 to 8, for each value of the ratio Ra = a / b between the outer diameter a of the first core region and the outer diameter b of the second core region, the relationship between the chromatic dispersion D _DCF and the slope compensation rate η is shown. It is shown.

FIG. 3 shows the relative refractive index difference Δn of the first core region.
₁ is + 1.2%, and the relative refractive index difference Δn ₂ of the second core region is −0.5%. In FIG. 4, the relative refractive index difference Δn ₁ of the first core region is + 1.5%, and the relative refractive index difference Δn ₂ of the second core region is −0.5%. In FIG. 5, the relative refractive index difference Δn ₁ of the first core region is + 1.7%, and the relative refractive index difference Δn ₂ of the second core region is −0.5%. FIG.
In this example, the relative refractive index difference Δn ₁ of the first core region is set to + 2.0%, and the relative refractive index difference Δn ₂ of the second core region is set to −0.5%. In FIG. 7, the relative refractive index difference Δn ₁ of the first core region is set to + 2.5%, and the relative refractive index difference Δn ₂ of the second core region is set to −.
0.5%. In FIG. 8, the relative refractive index difference Δn ₁ of the first core region is set to + 1.5%, and the relative refractive index difference Δn ₂ of the second core region is set to −0.7%.

As can be seen from these figures, the dispersion compensating optical fiber 21 is designed so that the relative refractive index difference between the first core region and the second core region and the value of the ratio Ra are appropriately designed to obtain the chromatic dispersion D. _The slope compensation ratio for the transmission path optical fiber 30 for which _DCF and dispersion are to be compensated can be set to a desired value, and at a wavelength of 1500 nm, the chromatic dispersion D _DCF can be -30 ps / nm / km or less, The ratio (S _DCF / D _DCF ) is -0.08 / nm
To + 0.05 / nm, and the slope compensation ratio can be 50% to 150%. Also,
The cutoff wavelength can also be set to 1.4 μm or less, whereby the dispersion compensating optical fiber 21 performs a single mode operation even in the wavelength band of the Raman amplification pumping light of 1.4 μm.

FIG. 9 is a graph showing the wavelength dependence of the transmission loss of the dispersion compensating optical fiber 21 according to the present embodiment.
This figure also shows the wavelength dependence of the transmission loss of the conventional dispersion compensating optical fiber, the range of the S band, that is, the Raman amplification band, and the Raman amplification capable of Raman amplifying the S band signal light. The position of the wavelength of the excitation light for use is indicated by an upward arrow. The conventional dispersion compensating optical fiber shown in this figure has an excess loss of about 0.4 dB / km due to the OH group in the wavelength band of 1.4 μm, whereas the dispersion compensating optical fiber 21 according to the present embodiment has OH in the wavelength band of 1.4 μm
The excess loss due to the radical is so small that it is almost negligible. In the dispersion compensating optical fiber 21 according to the present embodiment, the transmission loss at a wavelength of 1500 nm is about 0.3 dB / km and 1 dB / km or less.

FIG. 10 shows the chromatic dispersion characteristic of the dispersion compensating optical fiber 21 and the chromatic dispersion characteristic of the transmission optical fiber 30, and the optical transmission line including the dispersion compensating optical fiber 21 and the transmission optical fiber 30 according to the present embodiment. 5 is a graph showing the overall chromatic dispersion characteristics of FIG. The length ratio between the dispersion compensating optical fiber 21 and the transmission optical fiber 30 was adjusted such that the entire chromatic dispersion of the optical transmission line became 0 at a wavelength of 1500 nm. As can be seen from this figure, at a wavelength of 1500 nm, the chromatic dispersion and the dispersion slope of the transmission optical fiber 30 are compensated by the dispersion compensating optical fiber 21, and the optical transmission line including the dispersion compensating optical fiber 21 and the transmission optical fiber 30 is used. Has a small absolute value of the chromatic dispersion over a wide wavelength band of the S band.

As described above, if the dispersion compensating optical fiber 21 and the optical transmission line according to the present embodiment are used, the Raman amplification pumping light output from the Raman amplification pumping light source 23 transmits the dispersion compensating optical fiber 21 with low loss. Therefore, the light propagates from the dispersion compensating optical fiber 21 to the transmission optical fiber 30 and is supplied over a wide range of the optical transmission line. Therefore, the S-band signal light propagating in the optical transmission line is Raman-amplified with high efficiency. Further, the optical transmission line including the transmission optical fiber 30 and the dispersion compensating optical fiber 21 has a small absolute value of chromatic dispersion over the entire S-band wavelength band.
The transmission quality of the band signal light is excellent.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, the refractive index profile of the dispersion compensating optical fiber 21 is not limited to the one shown in FIG. 2, but may be another refractive index profile as shown in FIG. The refractive index profile shown in FIG. 11A is the same as that shown in FIG. Each of the refractive index profiles shown in FIGS. 11A to 11N has a core portion 110 and a cladding region 120, and the core portion 110 has various shapes. The optical fiber preform for manufacturing the dispersion compensating optical fiber having the refractive index profiles shown in FIGS. 11A to 11I and 11N can be manufactured by the manufacturing method described above. Manufacture of a dispersion-compensating optical fiber having the refractive index profiles shown in FIGS. 11J to 11M (the core portion 110 in which the central core region including the optical axis center has a lower refractive index than the surrounding region). The optical fiber preform is manufactured by the VAD method for the central core region, and is manufactured by the rod-in collapse method and the VAD method or the OVD method for the other regions. Alternatively, the central core region is manufactured by the MCVD method, and the other regions are manufactured by the VAD method.

[0030]

As described above in detail, the dispersion compensating optical fiber according to the present invention has a chromatic dispersion of -30 ps / nm / km or less at a wavelength of 1500 nm, and a ratio of the chromatic dispersion D to the dispersion slope S. (S / D) is -0.0
8 / nm to + 0.05 / nm, the polarization mode dispersion is 0.3 ps / km ^1/2 or less, and the transmission loss is 1 dB /
km or less, and the excess loss due to the OH group in the wavelength band of 1.4 μm is 0.2 dB / km or less. When this dispersion compensating optical fiber is used, the chromatic dispersion and dispersion slope of the transmission optical fiber are compensated in the S band, and the absolute value of the chromatic dispersion of the optical transmission line including the transmission optical fiber and the dispersion compensating optical fiber is reduced. , S-band signal light. When the Raman amplification pumping light (wavelength 1.4 μm band) is supplied to the dispersion compensating optical fiber, the Raman amplification pumping light propagates through the dispersion compensating optical fiber with low loss and propagates through the dispersion compensating optical fiber. The S-band signal light is Raman-amplified with high efficiency.

In the dispersion compensating optical fiber according to the present invention, when the cutoff wavelength is less than 1.4 μm,
The single mode operation is performed even in the wavelength band of 1.4 μm of the Raman amplification pump light capable of pumping the S band signal light.

Further, when the dispersion compensating optical fiber according to the present invention is covered with a hermetic coat, it is possible to prevent H ₂ from entering and suppress an increase in loss.

An optical transmission line according to the present invention is one in which a transmission optical fiber and the above-mentioned dispersion compensating optical fiber according to the present invention are connected. According to this optical transmission line, in the S band, the chromatic dispersion and the dispersion slope of the transmission optical fiber are compensated by the dispersion compensating optical fiber, and the absolute value of the chromatic dispersion of the optical transmission line including the transmission optical fiber and the dispersion compensating optical fiber is obtained. The value is small, which is suitable for transmitting S-band signal light. When the Raman amplification pump light (wavelength: 1.4 μm band) is supplied to the dispersion compensating optical fiber, the Raman amplification pump light propagates through the dispersion compensating optical fiber with low loss. Since the pumping light for Raman amplification propagates over a wide area of the optical transmission line including the dispersion compensating optical fiber, the S-band signal light propagating through the optical transmission line is Raman amplified with high efficiency.

Further, the optical transmission line according to the present invention comprises a Raman amplification pumping light supply means for supplying Raman amplification pumping light for Raman amplification of the signal light propagating through the optical transmission line to the optical transmission line. Further provision. In this case, the Raman amplification pumping light supply means (Raman amplification pumping light (wavelength 1.4 μm)
) Is supplied to the optical transmission path, and the S-band signal light propagating through the optical transmission path is Raman-amplified.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical transmission system 1 including a dispersion compensating optical fiber 12 and an optical transmission line according to an embodiment.

FIG. 2 is a diagram illustrating a refractive index profile of the dispersion compensating optical fiber 21 according to the present embodiment.

FIG. 3 is a graph showing a relationship between chromatic dispersion at a wavelength of 1550 nm and a slope compensation rate of the dispersion compensating optical fiber 21 according to the present embodiment.

FIG. 4 is a graph showing a relationship between chromatic dispersion at a wavelength of 1550 nm and a slope compensation rate of the dispersion compensating optical fiber 21 according to the present embodiment.

FIG. 5 is a graph showing the relationship between the chromatic dispersion at a wavelength of 1500 nm and the slope compensation rate of the dispersion compensating optical fiber 21 according to the present embodiment.

FIG. 6 is a graph showing the relationship between the chromatic dispersion at a wavelength of 1500 nm and the slope compensation rate of the dispersion compensating optical fiber 21 according to the present embodiment.

FIG. 7 is a graph showing the relationship between the chromatic dispersion at a wavelength of 1500 nm and the slope compensation rate of the dispersion compensating optical fiber 21 according to the present embodiment.

FIG. 8 is a graph showing a relationship between chromatic dispersion at a wavelength of 1500 nm and a slope compensation rate of the dispersion compensating optical fiber 21 according to the present embodiment.

FIG. 9 is a graph showing the wavelength dependence of the transmission loss of the dispersion compensating optical fiber 21 according to the present embodiment.

FIG. 10 shows a chromatic dispersion characteristic of the dispersion compensating optical fiber 21 and a chromatic dispersion characteristic of the transmission optical fiber 30 according to the embodiment;
4 is a graph showing the overall chromatic dispersion characteristics of the optical transmission line including the dispersion compensating optical fiber 21 and the transmission optical fiber 30.

FIG. 11 is a diagram illustrating another refractive index profile of the dispersion compensating optical fiber 21 according to the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical transmission system, 10, 20 ... Repeater, 21 ... Dispersion compensation optical fiber, 22 ... Optical coupler, 23 ... Raman amplification pumping light source, 24 ... EDFA, 30 ... Transmission optical fiber.

Continuation of the front page (72) Inventor Masashi Onishi 1 Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture F-term in the Yokohama Works, Sumitomo Electric Industries, Ltd. (reference) 2H050 AC09 AC14 AC28 AC71 AC75 AC81 AD01 2K002 AA02 AB30 BA01 CA15 DA10 HA24 5F072 AB07 AK06 KK30 QQ07

Claims (7)

[Claims] 1. At a wavelength of 1500 nm, chromatic dispersion is -30 ps / nm / km or less, and the ratio (S / D) of chromatic dispersion D to dispersion slope S is -0.08 / nm to +
0.05 / nm, and the polarization mode dispersion is 0.3 ps /
km ^1/2 or less, the transmission loss is 1 dB / km or less, and the excess loss due to OH groups in the wavelength band of 1.4 μm is 0.2.
A dispersion compensating optical fiber, which is not more than dB / km. 2. The dispersion compensating optical fiber according to claim 1, wherein the cutoff wavelength is 1.4 μm or less. 3. The dispersion-compensating optical fiber according to claim 1, wherein the optical fiber is covered with a hermetic coat. 4. The chromatic dispersion at a wavelength of 1500 nm is +
2ps / nm / km~ + 8ps / nm / km at and dispersion slope is 0.055ps / nm ² /km~0.065
^2. The dispersion compensator according to claim 1, wherein the transmission optical fiber has a length of ps / nm ² / km, and has a length connected to the transmission optical fiber and having a slope compensation rate of 50% to 150% with respect to the transmission optical fiber. An optical transmission path, comprising: an optical fiber. 5. The wavelength dispersion at a wavelength of 1500 nm is-
3ps / nm / km~ + 2ps / nm / km at and dispersion slope is 0.085ps / nm ² /km~0.095
^2. The dispersion compensation according to claim 1, wherein the transmission optical fiber has a length of ps / nm ² / km and is connected to the transmission optical fiber and has a slope compensation ratio of 50% to 150% with respect to the transmission optical fiber. An optical transmission path, comprising: an optical fiber. 6. The wavelength dispersion at a wavelength of 1500 nm is-
1ps / nm / km~ + 5ps / nm / km at and dispersion slope is 0.040ps / nm ² /km~0.050
^2. The dispersion compensation according to claim 1, wherein the transmission optical fiber has a length of ps / nm ² / km and is connected to the transmission optical fiber and has a slope compensation ratio of 50% to 150% with respect to the transmission optical fiber. An optical transmission line, comprising: an optical fiber. 7. The light according to claim 4, further comprising a Raman amplification pumping light supply unit that supplies Raman amplification pumping light for Raman amplification of the signal light. Transmission path.