JP2002182056A - Dispersion compensating optical fiber, optical transmission line including it and dispersion compensating module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersion compensating optical fiber capable of compensating the wavelength dispersion and dispersion slope of a non-zero dispersion shifting optical fiber with a short length. SOLUTION: The dispersion compensating optical fiber (100) has a wavelength dispersion of -40 ps/nm/km or less and the ratio (SDCF/DDCF) of the dispersion slope SDCF to wavelength dispersion DDCF being 0.005/km or more in a wavelength of 1550 nm and is composed of a core (110), a first clad (121) having a refractive index lower than that of the core (110), a second clad (122) having a refractive index higher than that of the first clad (121) and a third clad having a refractive index lower than that of the second clad (122).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dispersion-compensating optical fiber for compensating chromatic dispersion and dispersion slope of a dispersion-shifted optical fiber, an optical transmission line including the dispersion-shifted optical fiber and the dispersion-compensating optical fiber, and the dispersion-compensating light. The present invention relates to a dispersion compensation module in which a fiber or the like is wound into a coil and modularized.

[0002]

2. Description of the Related Art Wavelength division multiplexing (WDM)
n Multiplexing) In optical transmission systems that perform optical transmission, in order to further increase the speed and capacity of optical communication, it is necessary to minimize the absolute value of the cumulative chromatic dispersion of the optical transmission line in a wide signal wavelength band. is important. Generally,
Since it is difficult with an optical transmission line using only one type of optical fiber, by connecting a plurality of types of optical fibers to form an optical transmission line, the absolute value of the accumulated chromatic dispersion of the optical transmission line over a wide band can be obtained. Reduction has been achieved.

For example, Japanese Unexamined Patent Publication No. 6-11620 discloses a standard single mode fiber (SMF) having a zero dispersion wavelength around 1.3 μm.
r) and a dispersion compensating optical fiber (DCF: Dispersion Compensating Fiber) for compensating chromatic dispersion at a wavelength of 1550 nm of this standard single mode optical fiber are connected to each other, and 1. A technique for reducing the absolute value of the accumulated chromatic dispersion in a 55 μm wavelength band is disclosed.

US Pat. No. 5,838,867 discloses a non-zero dispersion shifted optical fiber (NZDSF: Non-zero dispersion) having a small positive chromatic dispersion at a wavelength of 1550 nm.
rsionShift Fiber) and a dispersion-compensating optical fiber for compensating for chromatic dispersion and dispersion slope at a wavelength of 1550 nm of the dispersion-shifted optical fiber are connected to each other, and the accumulation in the 1.55 μm wavelength band of the optical transmission line formed by connecting them is performed. A technique for reducing the absolute value of chromatic dispersion is disclosed.

[0005] Here, the chromatic dispersion of a standard single mode optical fiber (SMF) at a wavelength of 1550 nm is represented by D
_SMF and the dispersion slope as S _SMF . The chromatic dispersion of the non-zero dispersion shifted optical fiber (NZDSF) at a wavelength of 1550 nm is represented by D _DSF, and the dispersion slope is represented by S _DSF . Further, a wavelength 155 of the dispersion compensating optical fiber (DCF) is used.
The chromatic dispersion at 0 nm is represented by D _DCF and the dispersion slope is represented by S _DCF . At this time, in order to reduce the absolute value of the accumulated chromatic dispersion in the optical transmission line in a wide band including the wavelength of 1550 nm, a dispersion compensating optical fiber (hereinafter, referred to as a compensating fiber) that compensates for both the chromatic dispersion and the dispersion slope of a standard single mode optical fiber. The “dispersion compensating optical fiber for SMF”) has a ratio (S S) of the dispersion slope S _DCF to the chromatic dispersion D _DCF .
_DCF / D _DCF ) is the ratio of the dispersion slope S _SMF to the chromatic dispersion D _SMF of the single mode optical fiber (S _SMF / D _SMF ).
Is required to be approximately equal to In addition, a dispersion compensating optical fiber (hereinafter, referred to as a “DSF dispersion compensating optical fiber”) that compensates for both the chromatic dispersion and the dispersion slope of the dispersion-shifted optical fiber has a ratio of dispersion slope S _DCF to chromatic dispersion D _DCF (S _DCF / D _DCF ) is the ratio (S _DSF) of the dispersion slope S _DSF to the chromatic dispersion D _DSF of the dispersion-shifted optical fiber.
/ D _DSF ).

[0006]

SUMMARY OF THE INVENTION The present inventors have studied the conventional optical transmission line in detail and found the following problems. That is, compared to a standard single mode optical fiber, the dispersion shifted optical fiber has a wavelength of 1550 nm.
_{Has a} large ratio (S _DSF / D _DSF ). Therefore, as compared with the dispersion compensating optical fiber for SMF, the dispersion compensating optical fiber for DSF needs to have a larger ratio (S _DCF / D _DCF ) at a wavelength of 1550 nm.

The dispersion compensating optical fiber for SMF disclosed in Japanese Patent Application Laid-Open No. 6-11620 is a standard single mode optical fiber having a zero dispersion wavelength near 1.3 μm and a large chromatic dispersion at 1550 nm. Compensates for chromatic dispersion, and has negative chromatic dispersion having a large absolute value. Therefore, this SMF dispersion compensating optical fiber is suitable for compensating the chromatic dispersion of a standard single mode optical fiber. However, this SMF
The dispersion compensating optical fiber is not sufficient to compensate for the dispersion slope.

On the other hand, the dispersion compensating optical fiber for DSF disclosed in US Pat. No. 5,838,867 has a wavelength of 1550.
Both the chromatic dispersion and the dispersion slope of a non-zero dispersion shifted optical fiber having a small positive chromatic dispersion in nm can be compensated. However, since the dispersion compensating optical fiber for DSF has a small absolute value of the chromatic dispersion, a long dispersion compensating optical fiber for DSF is required to compensate for both the chromatic dispersion and the dispersion slope of the non-zero dispersion shifted optical fiber. Becomes

For example, in Reference 1, "S. Bigo, et al.," 1.5
Terabit / s WDM transmission of 150 channels at 10 G
bit / s over 4x100km of TeraLight ^TM fiber ", ECOC'99,
The non-zero dispersion shifted optical fiber disclosed in "PD (1999)" has a wavelength of +8 ps / nm / km at a wavelength of 1550 nm.
And a dispersion slope of +0.06 ps / nm ² / km. On the other hand, reference 2 “DW Peckham, et a
l., "Reduced dispersionslope, non-zero dispersion
fiber ", ECOC'98, pp. 139-140 (1998)", a chromatic dispersion of +4 ps / nm / km and a wavelength of +0.046 at a wavelength of 1550 nm.
It has a dispersion slope of ps / nm ² / km. Non-zero dispersion shifted optical fiber 80k disclosed in these documents
To compensate for both chromatic dispersion and dispersion slope of m
A dispersion compensating optical fiber for DSF having a length of 8 km to 16 km is required.

In general, a dispersion compensating optical fiber for DSF is liable to leak the fundamental mode light even with a slight bending.
Since the bending loss of the fundamental mode light is large, the transmission loss increases when the cable is laid and laid or wound around a coil to form a dispersion compensation module. Therefore, in an optical transmission system in which a signal is propagated through an optical transmission line in which a dispersion-shifted optical fiber and a DSF dispersion compensating optical fiber are connected to perform optical communication, transmission loss in the optical transmission line is large, so that the The length of the section cannot be increased, and it is not possible to further increase the speed and capacity of optical communication.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a dispersion compensating optical fiber capable of compensating chromatic dispersion and dispersion slope of a non-zero dispersion shifted optical fiber in a short length. A low transmission loss optical transmission line including a shift optical fiber and a dispersion compensating optical fiber,
Another object of the present invention is to provide a dispersion compensating module having a low transmission loss, in which the dispersion compensating optical fiber is wound into a coil and modularized.

[0012]

A dispersion compensating optical fiber according to the present invention has a wavelength of 1550 nm and a wavelength of -40 ps.
/ Nm / km and a wavelength dispersion D _DCF, 0.005 / n
m, the dispersion slope S for the chromatic dispersion D _{DCF
It has} a ratio of _DCF (S _DCF / D _DCF ). With this configuration,
Since the effective sectional area is easily enlarged, the occurrence of the nonlinear phenomenon is effectively suppressed. In the dispersion compensating optical fiber according to the present invention, the chromatic dispersion D _DCF is −100 ps / nm /
km and -40 ps / nm / km and the ratio of the dispersion slope S _DCF to the chromatic dispersion D _DCF (S _DCF / D
_DCF ) is preferably 0.005 / nm or more and 0.015 / nm or less. The chromatic dispersion D _DCF is negative and the absolute value is large, and the dispersion slope S for the chromatic dispersion D _{DCF is
Since the DCF} ratio (S _DCF / D _DCF ) is within the above numerical range, the dispersion compensating optical fiber compensates the chromatic dispersion and dispersion slope of the dispersion-shifted optical fiber in a short wavelength in a wide wavelength band including a wavelength of 1550 nm. be able to.

The dispersion compensating optical fiber according to the present invention has a wavelength of 1550 nm, preferably 16 μm ² or more,
It has an effective area of 0 μm ² or more. In this case, it is possible to suppress the occurrence of four-wave mixing and to suppress the waveform deterioration of the propagating signal.

The dispersion compensating optical fiber according to the present invention comprises:
1.2 μm or more and 1.8 μm or less, preferably 1.4
It has a cutoff wavelength of not less than μm and not more than 1.8 μm. Also, the dispersion compensating optical fiber according to the present invention has a transmission loss of 0.5 dB / km or less at a wavelength of 1550 nm. In this case, since the cutoff wavelength is longer than the conventional one, the increase in bending loss is suppressed. However, the loss is low.

The dispersion compensating optical fiber according to the present invention preferably has a core region extending along a predetermined axis and having a first refractive index, and a first cladding region provided on the outer periphery of the core region. The cladding region is provided on the outer periphery of the core region and has a second refractive index lower than the first refractive index.
A first cladding having a refractive index, a second cladding provided on the outer periphery of the first cladding and having a third refractive index higher than the second refractive index, and a third refraction provided on the outer periphery of the second cladding. A third cladding having a fourth refractive index lower than the index. The core region is 0.8% or more and 2.% based on the fourth refractive index of the third cladding.
It has a relative refractive index difference of 0% or less, more preferably 0.8% or more and 1.5% or less. The first cladding has a relative refractive index difference of -0.4% or less based on the fourth refractive index of the third cladding. These cases are suitable for realizing a dispersion compensating optical fiber having the above characteristics.

In the dispersion compensating optical fiber according to the present invention, when the outer diameter of the second cladding changes by 2%, the ratio (S
_DCF / D _DCF ) preferably varies by no more than 10%.
In this case, a dispersion compensating optical fiber having desired wavelength dispersion characteristics can be easily manufactured.

On the other hand, the transmission loss is reduced by shortening the fiber length.
To reduce the dispersion supplementary optical fiber according to the present invention,
-250ps / nm / km or more and -120ps / nm
/ Km or less chromatic dispersion D_DCF, 0.005 / nm or less
Some chromatic dispersion D_DCFDispersion slope S for_DCFRatio
(S_DCF/ D_DCF) And 10 μm^TwoAbove and 20μ
m ^TwoHereinafter, preferably (20− | D_DCF| / 25) or more
One (23- | D_DCF| / 25)
Is better. In areas where the absolute value of dispersion is large
It is necessary to reduce the size of the effective area
You. In addition, the dispersion compensating optical fiber is 1.0 dB / k.
m or less. Further, the dispersion compensating optical fiber
Fiber is, as described above, the core region and the first to third cracks.
Having a cladding region including
2.0% or more and 3.0% or less based on 3 clads
Relative refractive index difference, the first cladding is based on the third cladding
And has a relative refractive index difference of -0.4% or less.

An optical transmission line according to the present invention includes a relay section in which the dispersion compensating optical fiber is laid, and a dispersion-shifted optical fiber fusion-spliced to the dispersion compensating optical fiber. At a wavelength of 1550 nm, the dispersion-shifted optical fiber has +2 ps / nm / km or more and +10 ps / nm /
chromatic dispersion of less than km and +0.04 ps / nm ² / km
It has a dispersion slope of not less than +0.12 ps / nm ² / km. When these dispersion compensating optical fiber and dispersion shift optical fiber are connected to each other at a predetermined length ratio,
The entire optical transmission line constituted by these components has a wavelength of 1 wavelength.
At 550 nm, it has a small average chromatic dispersion and a small absolute dispersion slope. This allows
The optical transmission line as a whole has a small average chromatic dispersion and a small average transmission loss in a wide wavelength band including a wavelength of 1550 nm.

The entire optical transmission line according to the present invention has a deviation (= maximum value−minimum value) of 0.2 ps / nm / km or less in a wavelength band (C band) of 1535 nm or more and 1560 nm or less. Has an average chromatic dispersion. It is preferable that the average chromatic dispersion viewed from the whole has a deviation of 0.2 ps / nm / km or less in a wavelength band (C band and L band) of 1535 nm or more and 1600 nm or less. In such a case, in an optical transmission system that realizes optical communication by propagating a signal to an optical transmission line, the optical transmission line has a low average transmission loss, a small absolute value of average chromatic dispersion, and a wide wavelength including a wavelength of 1550 nm. Optical transmission at a high bit rate is possible in a band (including the C band and the L band). Therefore, this optical transmission system
The length of the relay section can be increased, and the speed and capacity of optical communication can be further increased.

The dispersion compensating module according to the present invention is characterized in that the dispersion compensating optical fiber is wound into a coil to form a module. In the dispersion compensation module in which the dispersion compensation optical fiber is modularized, the dispersion compensation optical fiber compensates for the chromatic dispersion and dispersion slope of the dispersion shift optical fiber laid in the repeater section. By setting an appropriate length ratio, at a wavelength of 1550 nm, the absolute value of the average chromatic dispersion as viewed from the whole becomes smaller, and the absolute value of the average dispersion slope as viewed from the whole becomes smaller. This allows
In the entire dispersion-shifted optical fiber and the dispersion compensation module, the absolute value of the average chromatic dispersion is reduced and the average transmission loss is reduced in a wide wavelength band including a wavelength of 1550 nm.

In the dispersion compensation module according to the present invention, the dispersion compensation amount at a wavelength of 1550 nm is -640 ps / n.
m, 1535 nm or more and 1565 nm or less, more preferably 1535 nm or more and 1610 nm
It has a total loss of 7 dB or less in the following wavelength bands. In the dispersion compensation module according to the present invention, the dispersion compensation amount at the wavelength of 1550 nm is -320 ps / nm.
When 1535 nm or more and 1565 nm or less,
More preferably, in the wavelength band of 1535 nm or more and 1610 nm or less, the total loss is 3 dB or less. In an optical transmission system having such a dispersion compensation module, a wide wavelength band including a wavelength of 1550 nm (a wavelength band including at least the C band and further including the L band).
, The average transmission loss is small, the absolute value of the average chromatic dispersion is small, the average transmission loss is small, the absolute value of the average chromatic dispersion is small, and optical transmission at a high bit rate becomes possible. Therefore, in this optical transmission system, the relay section can be lengthened, and the speed and capacity of optical communication can be further increased.

Further, according to the present invention, there is provided a dispersion compensating optical fiber.
At a wavelength of 1550 nm, -40 ps / nm /
wavelength dispersion D less than km_DCFAnd at 0.005 / nm or more
Some chromatic dispersion D_DCFDispersion slope S for_DCFRatio
(S_DCF/ D_DCF) And 16 μm ^TwoAbove, more preferably
20 μm^TwoIt is desirable to have the effective area described above. Wavelength 1
In a wide wavelength band including 550 nm, this dispersion compensation
The optical fiber is the chromatic dispersion and dispersion of the dispersion-shifted optical fiber.
Not only can the slope be compensated for short,
Suppress the generation of four-wave mixing and reduce the waveform deterioration of the propagating signal.
This is because it can be suppressed.

The dispersion compensating optical fiber according to the present invention has a chromatic dispersion D _{DCF of} -40 ps / nm / km or less at a wavelength of 1550 nm, and a dispersion slope S _DCF of chromatic dispersion D _DCF of not less than 0.005 / nm. Ratio (S _DCF /
D _DCF ) and a transmission loss of 0.5 dB / km or less. This dispersion compensating optical fiber can not only compensate the chromatic dispersion and dispersion slope of the dispersion-shifted optical fiber in a short wavelength in a wide wavelength band including the wavelength of 1550 nm, but also has a low dispersion even when it is cabled or modularized. Loss.

[0024]

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 diagram showing a schematic configuration of an optical transmission system including an optical transmission line 30 according to the present invention. In this optical transmission system 1, a station (transmitting station or relay station) 1
An optical transmission line 30 is laid in a relay section between 0 and a station (receiving station or relay station) 20. This optical transmission line 30
Is composed of a dispersion-shifted optical fiber 31 and a dispersion-compensating optical fiber 32 which are fusion-spliced to each other. In this optical transmission system 1, 1.
The signal having a plurality of wavelengths in the 55 μm wavelength band propagates through the dispersion-shifted optical fiber 31 and the dispersion-compensating optical fiber 32 in order, arrives at the station 20, and is sent to the station 2 in order to be sent further downstream.
0 or amplified at station 20.

The dispersion-shifted optical fiber 31 has a wavelength of 155.
An optical fiber mainly composed of silica having a small positive wavelength dispersion at 0 nm. This dispersion-shifted optical fiber 31
Is that at a wavelength of 1550 nm, the chromatic dispersion D _DSF is +2.
ps / nm / km to +10 ps / nm / km, dispersion slope S _DSF is +0.04 ps / nm ² / km to +0.12
It is ps / nm ² / km, and transmission loss is about 0.20 dB / km.

The dispersion compensating optical fiber 32 according to the present invention
Is at a wavelength of 1550 nm of the dispersion-shifted optical fiber 31.
Silica to compensate for chromatic dispersion and dispersion slope
An optical fiber as a component. This dispersion compensating optical fiber
32 indicates a chromatic dispersion D at a wavelength of 1550 nm._DCFBut
-40 ps / nm / km or less, wavelength dispersion D_DCFAgainst
Dispersion slope S_DCFRatio (S_DCF/ D_DCF) Is 0.005
/ Nm or more. Preferably, the dispersion compensating optical fiber
The beam 32 has a chromatic dispersion D at a wavelength of 1550 nm. _DCF
Is from -100 ps / nm / km to -40 ps / nm / k
m, wavelength dispersion D_DCFDispersion slope S for_DCFRatio (S
_DCF/ D_DCF) Is 0.005 / nm to 0.015 / nm
is there. The dispersion compensating optical fiber 32 has a wavelength
16 μm at 50 nm^TwoAbove, preferably 20 μm^Two
The effective area described above, 1.2 μm to 1.8 μm, preferably
Is a cut-off wavelength of 1.4 μm to 1.8 μm, and a wavelength of 15 μm.
Has transmission loss of less than 0.5 dB / km at 50 nm
I do.

Further, the dispersion compensating optical fiber 32 has a wavelength of -250 ps / nm / km to 1550 nm.
Wavelength dispersion D _DCF of 120 ps / nm / km, 0.005
/ Km or more, the ratio of the dispersion slope S _DCF to the chromatic dispersion D _DCF (S _DCF / D _DCF ), 10 μm ^{2 to} 20 μm ²
Has an effective sectional area of The dispersion compensating optical fiber 32
Is from 1.2 μm to 1.8 μm, preferably from 1.4 μm to
It has a transmission loss of 1.0 dB / km or less at a cutoff wavelength of 1.8 μm and a wavelength of 1550 nm.

Since the chromatic dispersion D _DCF and the dispersion slope S _DCF are within the above numerical ranges, the dispersion compensating optical fiber 32 having such characteristics has the chromatic dispersion of the dispersion shifted optical fiber 31 in a wide wavelength band including the wavelength of 1550 nm. And the dispersion slope can be compensated for on a short scale. In addition, since the dispersion compensating optical fiber 32 has the chromatic dispersion in the above numerical range and has a sufficient effective area, it is possible to suppress the occurrence of four-wave mixing and to suppress the waveform deterioration of the signal to be propagated. . Further, this dispersion compensating optical fiber 32
Since the cutoff wavelength is in the above numerical range, the increase in bending loss can be suppressed, and the transmission loss is in the above numerical range. 30 is low loss.

The optical transmission line 30 in which the dispersion-shifted optical fiber 31 and the dispersion-compensating optical fiber 32 are fusion-spliced at an appropriate length ratio has a small absolute value of the average chromatic dispersion as a whole at a wavelength of 1550 nm. The absolute value of the average dispersion slope viewed from the whole is also small. As a result, the optical transmission path 30
In a wide wavelength band including the wavelength of 1550 nm, the absolute value of the average chromatic dispersion viewed from the whole becomes small. The optical transmission line 30 also has a small average transmission loss as viewed from the whole. The deviation of the average chromatic dispersion of the entire optical transmission line 30 is 1535 nm to 15 nm.
0.2 ps / in the 60 nm wavelength band (C band)
nm / km or less.
More preferably, it is 0.2 ps / nm / km or less in a 1600 nm wavelength band (C band and L band). The optical transmission system 1 that performs optical communication by propagating a signal to the optical transmission line 30 in such a wide wavelength band including a wavelength of 1550 nm (a wavelength band including at least the C band and further including the L band). The average transmission loss of the transmission line 30 is small, the absolute value of the average chromatic dispersion is small, and optical transmission at a high bit rate is possible. Therefore, the optical transmission system 1 can lengthen the relay section,
The speed and capacity of optical communication can be further increased.

FIG. 2 is a diagram showing a schematic configuration of an optical transmission system 2 in which a dispersion-shifted optical fiber 31 is laid as an optical transmission line and a dispersion-compensating optical fiber 32 is disposed in the station 20 as a dispersion-compensating module. This optical transmission system 2
In a relay section between a station (transmitting station or relay station) 10 and a station (receiving station or relay station) 20, a dispersion-shifted optical fiber 31 is laid as an optical transmission line.
In this optical transmission system 2, signals of a plurality of wavelengths in the 1.55 μm wavelength band transmitted from the station 10 reach the station 20 by propagating through the dispersion-shifted optical fiber 31, which is an optical transmission line. At the station 20, these signals are amplified by an optical amplifier 21, dispersion-compensated by a dispersion-compensating optical fiber 32 as a dispersion-compensating module, further amplified by an optical amplifier 22, and then received or sent further downstream.

The dispersion-shifted optical fiber 31 applied to the optical transmission line in the optical transmission system 2 of FIG. 2 is different from the dispersion-shifted optical fiber 31 used as a part of the optical transmission line in the optical transmission system 1 of FIG. It has similar characteristics.
The dispersion compensating optical fiber 32 applied as the dispersion compensating module in the optical transmission system 2 of FIG.
Has the same characteristics as the dispersion compensating optical fiber 32 used as a part of the optical transmission line in the optical transmission system 1 of FIG. However, in the optical transmission system 2 shown in FIG. 2, the dispersion compensating optical fiber 32 is wound around a bobbin in a coil shape to be modularized and provided in the station 20.

Since the dispersion compensating optical fiber 32 having the above-described characteristics has the chromatic dispersion D _DCF and the dispersion slope S _DCF within the above numerical ranges, the chromatic dispersion of the dispersion-shifted optical fiber 31 in a wide wavelength band including the wavelength of 1550 nm. And the dispersion slope can be compensated for on a short scale. Also,
Since the dispersion compensating optical fiber 32 has a chromatic dispersion in the above numerical range and a sufficient effective area, it is possible to suppress the generation of four-wave mixing and to suppress the waveform deterioration of the propagating signal. Further, the dispersion compensating optical fiber 32
Since the cutoff wavelength is in the above-mentioned numerical range, the increase in bending loss can be suppressed, and the transmission loss is in the above-mentioned numerical range. Loss.

A dispersion-shifted optical fiber 3 as an optical transmission line
1 and a dispersion compensating optical fiber 3 as a dispersion compensating module
2 each have a wavelength of 15 when each has a length.
At 50 nm, the absolute value of the average chromatic dispersion is small, and the absolute value of the average dispersion slope is also small. As a result, in the dispersion-shifted optical fiber 31 and the dispersion-compensating optical fiber 32 as a whole, the absolute value of the average chromatic dispersion is reduced in a wide wavelength band including the wavelength of 1550 nm, and the average transmission loss is also reduced. The deviation of the average chromatic dispersion from the whole is
It is 0.2 ps / nm / km or less in a wavelength band of 1535 nm to 1560 nm (C band), and preferably 0.2 ps / nm / km or less in a wavelength band of 1535 nm to 1600 nm (C band and L band).

On the other hand, when the dispersion compensation amount at a wavelength of 1550 nm is -640 ps / nm, the dispersion compensating optical fiber 32 as a dispersion compensation module has a wavelength of 1535 nm to 1535 nm.
The total loss is 7 dB or less in the wavelength band (C band) of 1565 nm, and more preferably 1535 nm to 16 dB.
Total loss is 7 dB or less in a 10 nm wavelength band (C band and L band). The dispersion compensating optical fiber 32 as a dispersion compensating module has a wavelength of 1550 nm.
Is −320 ps / nm,
In a wavelength band (C band) of 1535 nm to 1565 nm, the total loss is 3 dB or less, and more preferably 15 dB or less.
The total loss is 3 dB or less in a wavelength band (C band and L band) of 35 nm to 1610 nm.

In this optical transmission system 2, the wavelength 15
In a wide wavelength band including 50 nm (a wavelength band including at least the C band and also including the L band), the average transmission loss is small, the absolute value of the average chromatic dispersion is small, and high bit rate optical transmission is possible. . Therefore, the optical transmission system 2 can lengthen the relay section, and can further increase the speed and capacity of optical communication.

FIGS. 3A and 3B show the sectional structure and the refractive index profile of the dispersion compensating optical fiber according to the present invention.

The optical fiber 100 shown in FIG. 3A corresponds to the dispersion compensating optical fiber 32, and includes a core region 110 extending along a predetermined axis, and a cladding region 120 provided so as to surround the outer periphery of the core region 110. And The core region 110 has a first refractive index n ₁ and an outer diameter 2a. Further, the cladding region 120 includes a first cladding 121 having a second refractive index n ₂ (<n ₁ ) and an outer diameter 2b, and a third refractive index n provided to surround the outer periphery of the first cladding 121.
Second clad 1 having ₃ (> n ₂ , <n ₁ ) and outer diameter 2c
22 and the fourth cladding 122 provided on the outer periphery of the second cladding 122.
Third cladding 12 having refractive index n ₄ (<n ₃ ,> n ₂ )
3 is provided.

The refractive index profile 15 shown in FIG. 3B
0 indicates the refractive index of each part on the line L1 in FIG. 3A, and the regions 151, 152, 15 in the refractive index profile 150.
Reference numerals 3 and 154 denote the refractive indices of the core region 110, the first clad 121, the second clad 122, and the third clad 123, respectively, on the line L1.

[0040] In the dispersion compensating optical fiber 100 shown in FIGS. 3A and 3B, a third cladding 123 as a reference region, the relative refractive index difference [Delta] n ₁ of the core region 110, the relative refractive index difference [Delta] n ₂ of the first cladding 121 And the relative refractive index difference Δn ₃ of the second cladding 122 are given by the following equations.

[Formula 1] Here, n ₁ is the refractive index of the core region 110, n ₂ is the refractive index of the first cladding 121, n ₃ is the refractive index of the second cladding 122, n ₄ is the refractive index of the third cladding. In this specification, the relative refractive index difference of each part is expressed as a percentage, and each parameter in the above equation does not change in order. Therefore, the relative refractive index difference of the glass region having a lower refractive index than the third cladding 123 (reference region) is represented by a negative value.

In the dispersion compensating optical fiber 100, the third
Based on the refractive index n ₄ of the cladding 123, the core region 1
10 is from 0.8% to 2.0%, more preferably from 0.8% to 2.0%
The first clad 12 has a relative refractive index difference Δn ₁ of 1.5%.
No. 1 has a relative refractive index difference Δn ₂ of −0.4% or less.

Since the dispersion compensating optical fiber 100 has such a refractive index profile, its chromatic dispersion D _DCF ,
The ratio (S _DCF / D _DCF ), effective area, cut-off wavelength, and transmission loss are all within the above numerical ranges at a wavelength of 1550 nm. In order to obtain the dispersion compensating optical fiber 100 having such a refractive index profile, for example, based on silica glass, GeO ₂ is added to the core region 110, F element is added to the first cladding 121, and the second cladding is GeO ₂ is added to the region 122. Thereby, the refractive index profile 150 shown in FIG. 3B is realized, and the wavelength 1550n of the dispersion compensating optical fiber 100 is obtained.
The transmission loss at m can be reduced.

Next, a specific embodiment of the dispersion compensating optical fiber 32 according to the present invention will be described. Dispersion compensating optical fiber DC according to first to seventh embodiments described below
Each of F1 to DCF7 has a sectional structure of FIG. 3A and FIG.
Has a refractive index profile 150 of (1st Embodiment)

The dispersion compensating optical fiber D according to the first embodiment
In CF1, the relative refractive index difference Δn _{1 in the} core region is 1.2% with respect to the third clad 123, and the first clad 1
The relative refractive index difference of 21 [Delta] n ₂ is -0.50%, the relative refractive index difference [Delta] n ₂ of the second cladding 122 is 0.20%, the ratio of the outer diameter of each core region 110 and the second cladding 122 (2a / 2c) is 0.30, and the ratio (2b / 2c) of the outer diameter of each of the first cladding 121 and the second cladding 122 is 0.60. In the dispersion compensating optical fiber DCF1 according to the first embodiment, the outer diameter 2c of the second cladding 122 is 1
At 7.7 μm, at a wavelength of 1550 nm, −6
Wavelength dispersion D _DCF of 2.4 ps / nm / km, -0.44
Dispersion slope S _{DCF of} ps / nm ² / km, 24.4 μm
10 dB / m at an effective area of ^{2 and} a bending diameter of 20 mm
And a transmission loss of 0.30 dB / km.
The cut-off wavelength is 1224 nm, and the ratio (S _DCF / D _DCF ) at a wavelength of 1550 nm is 0.007.
1 / nm. (2nd Embodiment)

The dispersion compensating optical fiber D according to the second embodiment
In CF2, relative refractive index difference Δn ₁ of core region 110 is 1.3%, relative refractive index difference Δn ₂ of first cladding 121 is −0.50%, and second cladding 122 is based on third cladding 123. Has a relative refractive index difference Δn ₃ of 0.23%,
The ratio (2a / 2c) of the outer diameter of each of the core region 110 and the second cladding 122 is 0.27, and the ratio of the outer diameter of each of the first cladding 121 and the second cladding 122 (2b / 2).
c) was 0.55. When the outer diameter 2c of the second cladding 122 is 19.0 μm, the dispersion compensation optical fiber DCF2 according to the second embodiment has a wavelength dispersion D _DCF of −80.4 ps / nm / km at a wavelength of 1550 nm,
−0.59 ps / nm ² / km dispersion slope S _DCF , 2
3.9 μm ² effective cross-sectional area, 4 dB /
It has a bending loss of m and a transmission loss of 0.33 dB / km. The cutoff wavelength is 1576 nm, and the ratio (S _DCF / D _DCF ) at a wavelength of 1550 nm is 0.007.
3 / nm. (Third embodiment)

The dispersion compensating optical fiber D according to the third embodiment
In CF3, the relative refractive index difference Δn ₁ of the core region 110 is 1.7%, the relative refractive index difference Δn ₂ of the first cladding 121 is −0.50%, and the second cladding 122 is based on the third cladding 123. Has a relative refractive index difference Δn ₃ of 0.25%,
The ratio (2a / 2c) of the outer diameter of each of the core region 110 and the second cladding 122 is 0.23, and the ratio of the outer diameter of each of the first cladding 121 and the second cladding 122 (2b / 2).
c) is 0.53. The dispersion compensating optical fiber DCF3 according to the third embodiment has an outer diameter 2c of the second cladding 122.
Is 18.7 μm, the wavelength dispersion D _DCF of −83.7 ps / nm / km at the wavelength of 1550 nm, −
0.66 ps / nm ² / km dispersion slope S _DCF , 1
It has a bending loss of 0.2 dB / m and a transmission loss of 0.39 dB / km at an effective sectional area of 7.2 μm ² and a bending diameter of 20 mm. The cutoff wavelength was 1696 nm, and the ratio (S _DCF / D _DCF ) at a wavelength of 1550 nm was 0.0079 / nm.

FIG. 4 is a graph showing the relationship between chromatic dispersion and dispersion slope at a wavelength of 1550 nm of each of the dispersion compensating optical fibers according to the first to third embodiments. In FIG. 4, G110 shows a curve for the first embodiment, G210 shows a curve for the second embodiment, and G110
Numeral 310 indicates a curve for the third embodiment. here,
The relationship between the chromatic dispersion D _DCF and the dispersion slope S _DCF in the dispersion compensating optical fiber of each embodiment when the outer diameter 2c of the second clad 122 is changed is shown. As can be seen from the graph of FIG.
In each of the _{DCFs 3} , even if the outer diameter 2c of the second cladding 122 changes, the chromatic dispersion D _DCF is approximately −60.
Within the range of ps / nm / km to −10 ps / nm / km, the change in the ratio of the dispersion slope S _DCF to the chromatic dispersion D _DCF (S _DCF / D _DCF ) is small. In the dispersion compensating optical fiber DCF1 according to the first embodiment, when the outer diameter 2c of the second cladding 122 changes by 2%, the ratio (S
_DCF / D _DCF ) changes by 2.5% or less, and the range of chromatic dispersion D _DCF is −68 ps / nm while the change amount of the ratio (S _DCF / D _DCF ) is maintained at 10% or less. / Km
−−17 ps / nm / km. In the dispersion compensating optical fiber DCF2 according to the second embodiment, the second cladding 122
When the outer diameter 2c of the sphere changes by 2%, the ratio (S _DCF /
D _DCF ) changes by 9.0% or less, and further the ratio (S _DCF /
The range of the chromatic dispersion D _DCF is −81 ps / nm / km to −30 p while the variation of D _DCF is maintained at 10% or less.
s / nm / km. In the dispersion compensating optical fiber DCF3 according to the third embodiment, the outer diameter 2c of the second cladding 122
Is changed by 2%, the ratio (S _DCF / D _DCF ) becomes 4.0
% And the amount of change in the ratio (S _DCF / D _DCF ) is maintained at 10% or less, and the range of chromatic dispersion D _DCF is from −115 ps / nm / km to −62 ps / nm / km.
Becomes Thus, the outer diameter 2c of the second clad 122
If the change in the ratio (S _DCF / D _DCF ) to the change in% is 10% or less, a dispersion-compensating optical fiber having desired chromatic dispersion characteristics can be easily manufactured.

FIG. 5 is a graph showing the wavelength dependence of bending loss at a bending diameter of 140 mm for each of the dispersion compensating optical fibers according to the first to third embodiments. In FIG. 5, G120 indicates a curve for the first embodiment,
220 shows the curve for the second embodiment, G320
Indicates a curve for the third embodiment. At this time, the first
The outer diameter 2c of the second cladding 122 of the dispersion compensating optical fiber DCF1 according to the embodiment is 17.7 μm, and the second cladding 122 of the dispersion compensating optical fiber DCF2 according to the second embodiment.
The outer diameter 2c of the second cladding 122 of the dispersion compensating optical fiber DCF3 according to the third embodiment is 19.0 μm.
Was 18.7 μm. As can be seen from the graph of FIG. 5, each of the dispersion compensating optical fibers DCF1 to DCF3 has a small bending loss in a wavelength range of 1610 nm or less.

Therefore, the dispersion compensating optical fiber DCF1
To DCF3 are not only preferably used as the dispersion compensating optical fiber 32 applied as a part of the optical transmission line 30 of the optical transmission system 1 shown in FIG. 1, but also the optical transmission system shown in FIG. 2 is also suitably used as the dispersion compensating optical fiber 32 forming the second dispersion compensating module.
Thereby, chromatic dispersion can be compensated with low loss not only in the C band but also in the L band.

FIG. 6 is a graph showing the wavelength dependence of chromatic dispersion for the dispersion compensating optical fibers according to the first to third embodiments. Also in FIG. 6, G130 shows the curve for the first embodiment, G230 shows the curve for the second embodiment, G330 shows the curve for the third embodiment, and G1000 shows the above document 1. 4 shows a curve for a dispersion shifted optical fiber NZDSF. Here, the dispersion compensating optical fiber DCF1 according to the first embodiment
The outer diameter 2c of the second clad 122 is 17.7 μm,
The outer diameter 2c of the second cladding 122 of the dispersion compensating optical fiber DCF2 according to the embodiment is 19.0 μm, and the second cladding 122 of the dispersion compensating optical fiber DCF3 according to the third embodiment.
Has an outer diameter 2c of 18.7 μm.

FIG. 7 is a graph showing the wavelength dependence of the average chromatic dispersion as a whole when the dispersion compensating optical fiber and the dispersion shift optical fiber according to the first to third embodiments are connected. In FIG. 7, G140 is the first
6 shows a curve for a configuration in which the dispersion compensating optical fiber DCF1 according to the embodiment and the dispersion-shifted optical fiber NZDSF of FIG. 6 are connected, and G240 denotes the dispersion-compensating optical fiber DCF2 of the second embodiment and the dispersion-shifted light of FIG. FIG. 4 shows curves for a configuration in which a fiber NZDSF is connected;
G340 is the dispersion compensating optical fiber DC according to the third embodiment.
7 illustrates a curve for a configuration in which F3 and the dispersion-shifted optical fiber NZDSF of FIG. 6 are connected. In order to compensate the chromatic dispersion at a wavelength of 1550 nm of the dispersion-shifted optical fiber NZDSF having the chromatic dispersion characteristic shown in FIG. 6 and the length of 80 km, the dispersion compensating optical fiber D according to the first embodiment is used.
The CF1 needs a length of 10.3 km, and the dispersion compensating optical fiber DCF2 according to the second embodiment has a length of 8.0 km.
Length of the dispersion-compensating optical fiber DCF according to the third embodiment
3 required a length of 7.5 km.

The dispersion compensating optical fiber D according to the first embodiment
In the configuration in which the SF1 and the dispersion-shifted optical fiber NZDSF are connected, in the wavelength band (C band and L band) of 1535 nm to 1600 nm, the deviation of the average chromatic dispersion as a whole is 0.2 ps / nm / km or less. Was. In the configuration in which the dispersion compensating optical fiber DSF2 and the dispersion-shifting optical fiber NZDSF according to the second embodiment are connected, in the wavelength band (C band) of 1535 nm to 1560 nm, the deviation of the average chromatic dispersion as a whole is 0.
It was 2 ps / nm / km or less. Dispersion compensating optical fiber DSF3 and dispersion-shifting optical fiber N according to the third embodiment
In the configuration in which ZDSF is connected, 1535 nm to 15
In the wavelength band of 60 nm (C band), the deviation of the average chromatic dispersion as viewed from the whole was 0.2 ps / nm / km or less. Therefore, they have a bit rate of 40 Gb
/ S enables optical transmission over a relay distance of 400 km.

FIG. 8 is a diagram showing a schematic configuration of a dispersion compensating module including the dispersion compensating optical fiber according to the present invention. The dispersion compensating optical fiber 100 (corresponding to the dispersion supplementary optical fiber 32 according to the present invention) is housed in a case 300. Both ends of the fiber 100 are connected to a pigtail fiber 320 that reduces splice loss. In a state where the dispersion-compensating optical fiber DCF1 according to the first embodiment having a length of 10.3 km is wound with a bending diameter of 140 mm to form a dispersion-compensating module, the wavelength is 1550 nm.
Was 640 ps / nm, and the total loss was 4.1 dB (wavelength 1550 nm). The dispersion-compensating optical fiber D according to the second embodiment having a length of 8.0 km
Bending diameter 14 so that CF2 forms a dispersion compensation module
In a state of being wound at 0 mm, the dispersion compensation amount at a wavelength of 1550 nm is -640 ps / nm, and the total loss is 4.4.
dB (wavelength 1550 nm). In addition, length 7.
5 km dispersion-compensating optical fiber DCF according to the third embodiment
Bending diameter 140m so that 3 forms a dispersion compensation module
m, the amount of dispersion compensation at a wavelength of 1550 nm is -640 ps / nm, and the total loss is 4.1 dB.
(Wavelength 1550 nm).

The dispersion compensating optical fiber DCF1 according to the first embodiment is wound with a bending diameter of 140 mm to form a dispersion compensating module, and has a wavelength of 1550 nm.
Is −320 ps / nm,
The total loss (wavelength 1550 nm) was 2.3 dB. When the dispersion compensating optical fiber DCF2 according to the second embodiment is wound with a bending diameter of 140 mm to form a dispersion compensating module and the dispersion compensation amount at a wavelength of 1550 nm is -320 ps / nm, the total loss (wavelength 155
0 nm) was 2.5 dB. Further, in a state where the dispersion compensating optical fiber DCF3 according to the third embodiment is wound with a bending diameter of 140 mm to form a dispersion compensating module,
And the dispersion compensation amount at a wavelength of 1550 nm is -320.
When it was ps / nm, the total loss (wavelength 1550 nm) was 2.7 dB.

As described above, the dispersion compensating optical fiber DCF1
DCF3 can compensate for the chromatic dispersion and dispersion slope of the dispersion-shifted optical fiber NZDSF in a short wavelength and at a low loss in a wide wavelength band including a wavelength of 1550 nm. (Fourth embodiment)

The dispersion compensating optical fiber D according to the fourth embodiment
In CF4, the relative refractive index difference Δn ₁ of the core region 110 is 1.6%, the relative refractive index difference Δn ₂ of the first cladding 121 is −0.50%, and the second cladding 122 is based on the third cladding 123. Has a relative refractive index difference Δn ₃ of 0.24%,
The ratio (2a / 2c) of the outer diameter of each of the core region 110 and the second cladding 122 is 0.23, and the ratio of the outer diameter of each of the first cladding 121 and the second cladding 122 (2b / 2).
c) is 0.55. The dispersion compensating optical fiber DCF4 according to the fourth embodiment has an outer diameter 2c of the second cladding 122.
Is 19.2 μm, the wavelength dispersion D _DCF of −85.1 ps / nm / km at the wavelength of 1550 nm, −
0.83 ps / nm ² / km dispersion slope S _DCF , 1
It has an effective area of 8.1 μm ² , a bending loss of 0.9 dB / m and a transmission loss of 0.38 dB / km at a bending diameter of 20 mm. The cutoff wavelength was 1638 nm, and the ratio (S _DCF / D _DCF ) at a wavelength of 1550 nm was 0.0098 / nm.

FIG. 9 shows a dispersion compensating light beam according to the fourth embodiment.
Fiber chromatic dispersion and dispersion at 1550 nm wavelength
It is a graph which shows the relationship of a slope. In FIG. 9, G
Reference numeral 410 denotes a curve for the fourth embodiment. Where
When the outer diameter 2c of the second clad 122 is changed,
Chromatic dispersion D in the dispersion compensating optical fiber according to the embodiment
_DCFAnd dispersion slope S_DCFThe relationship is shown. FIG.
As can be seen from the graph of FIG.
In 4, the outer diameter 2c of the second clad 122 changed.
, The chromatic dispersion D_DCFIs approximately -102 ps /
If nm / km to -71 ps / nm / km, the ratio (S
_DCF/ D_DCF) Is maintained at 10% or less. this
In the dispersion compensating optical fiber DCF4 according to the fourth embodiment
Thus, the outer diameter 2c of the second cladding 122 has changed by 2%.
When the ratio (S_DCF/ D_DCF) Changes by less than 5.8%
You. The outer diameter 2c of the second cladding 122 has changed by 2%.
When the ratio (S_DCF/ D_DCF) Is less than 10%
If possible, a dispersion compensating optical fiber having preferable wavelength dispersion characteristics
Fiber can be easily manufactured.

FIG. 10 is a graph showing the wavelength dependence of the bending loss at a bending diameter of 140 mm for the dispersion compensating optical fiber according to the fourth embodiment. In FIG. 10, G42
0 indicates a curve for the fourth embodiment. At this time, the outer diameter 2c of the second cladding 122 of the dispersion compensating optical fiber DCF4 according to the fourth embodiment was 17.2 μm. As can be seen from the graph of FIG. 10, the dispersion compensating optical fiber DCF4 has a small bending loss in a wavelength range of 1610 nm or less.

Therefore, the dispersion compensating optical fiber DCF4
Is preferably used not only as the dispersion compensating optical fiber 32 applied as a part of the optical transmission line 30 of the optical transmission system 1 shown in FIG. 1 but also in the optical transmission system 2 shown in FIG. It is also suitably used as the dispersion compensating optical fiber 32 forming the compensating module, so that chromatic dispersion can be compensated with low loss not only in the C band but also in the L band.

FIG. 11 is a graph showing the wavelength dependence of chromatic dispersion for the dispersion compensating optical fiber according to the fourth embodiment. Also in FIG. 11, G430 indicates a curve for the fourth embodiment, and G430 indicates the chromatic dispersion of 4 ps / nm / km or less and 0.046 p
3 shows a curve for a non-zero dispersion shifted optical fiber NZDSF having a dispersion slope of s / nm ² / km or less. Here, the dispersion compensating optical fiber DCF4 according to the fourth embodiment
The outer diameter 2c of the second cladding 122 is 19.2 μm.

FIG. 12 is a graph showing the wavelength dependence of the average chromatic dispersion as a whole when the dispersion compensating optical fiber and the dispersion shift optical fiber according to the fourth embodiment are connected. In FIG. 12, G440 indicates a curve for a configuration in which the dispersion compensating optical fiber DCF4 according to the fourth embodiment and the dispersion-shifting optical fiber NZDSF of FIG. 11 are connected. The chromatic dispersion characteristics shown in FIG.
Dispersion-shifted optical fiber NZDSF having a length of 0 km
To compensate for the chromatic dispersion at a wavelength of 1550 nm,
The dispersion compensating optical fiber DCF4 according to the fourth embodiment requires a length of 4.4 km.

The dispersion compensating optical fiber D according to the fourth embodiment
In the configuration in which the SF4 and the dispersion-shifted optical fiber NZDSF are connected, in the wavelength band (C band and L band) of 1535 nm to 1600 nm, the deviation of the average chromatic dispersion as a whole is 0.2 ps / nm / km or less. Was. Therefore, they have a bit rate of 40 Gb / s
Thus, optical transmission exceeding a relay distance of 400 km is possible.

When the dispersion compensating optical fiber DCF4 according to the fourth embodiment having a length of 4.4 km is wound with a bending diameter of 140 mm to form a dispersion compensating module, the wavelength 15
The dispersion compensation amount at 50 nm was -640 ps / nm, and the total loss (wavelength 1550 nm) was 3.9 dB. Further, the dispersion compensating optical fiber DC according to the fourth embodiment
The bending diameter 140 is set so that F4 forms a dispersion compensation module.
When the film was wound in mm and the amount of dispersion compensation at a wavelength of 1550 nm was -320 ps / nm, the total loss (wavelength of 1550 nm) was 2.5 dB.

As described above, the dispersion compensating optical fiber DCF4
Can compensate for the chromatic dispersion and dispersion slope of the dispersion-shifted optical fiber NZDSF in a short wavelength and low loss in a wide wavelength band including a wavelength of 1550 nm. (Fifth embodiment)

The dispersion compensating optical fiber D according to the fifth embodiment
In CF5, the relative refractive index difference Δn ₁ of the core region 110 is 2.1%, the relative refractive index difference Δn ₂ of the first cladding 121 is −0.50%, and the second cladding 122 is based on the third cladding 123. Has a relative refractive index difference Δn ₃ of 0.20%,
The ratio (2a / 2c) of the outer diameter of each of the core region 110 and the second cladding 122 is 0.18, and the ratio of the outer diameter of each of the first cladding 121 and the second cladding 122 (2b / 2).
c) is 0.49. The dispersion compensating optical fiber DCF5 according to the fifth embodiment has an outer diameter 2c of the second cladding 122.
Is 19.4 μm, a wavelength dispersion D _DCF of −160.7 ps / nm / km at a wavelength of 1550 nm,
Dispersion slope S _{DCF of} -1.63 ps / nm ² / km, 1
It has an effective area of 5.7 μm ² , a bending loss of 1.8 dB / m and a transmission loss of 0.49 dB / km at a bending diameter of 20 mm. The cutoff wavelength was 1566 nm, and the ratio (S _DCF / D _DCF ) at a wavelength of 1550 nm was 0.0101 / nm. (Sixth embodiment)

The dispersion compensating optical fiber D according to the sixth embodiment
In CF6, the relative refractive index difference Δn ₁ of the core region 110 is 2.4%, the relative refractive index difference Δn ₂ of the first cladding 121 is −0.50%, and the second cladding 122 is based on the third cladding 123. Has a relative refractive index difference Δn ₃ of 0.40%,
The ratio (2a / 2c) of the outer diameter of each of the core region 110 and the second cladding 122 is 0.20, and the ratio of the outer diameter of each of the first cladding 121 and the second cladding 122 (2b / 2).
c) is 0.65. The dispersion compensating optical fiber DCF6 according to the sixth embodiment has an outer diameter 2c of the second cladding 122.
Is 16.0 μm, the wavelength dispersion D _DCF of −181.6 ps / nm / km at a wavelength of 1550 nm,
Dispersion slope S _{DCF of} -1.87 ps / nm ² / km, 1
It has an effective area of 3.8 μm ² , a bending loss of 0.5 dB / m and a transmission loss of 0.61 dB / km at a bending diameter of 20 mm. The cutoff wavelength was 1660 nm, and the ratio (S _DCF / D _DCF ) at a wavelength of 1550 nm was 0.0103 / nm. (Seventh embodiment)

The dispersion compensating optical fiber D according to the seventh embodiment
In CF7, the relative refractive index difference Δn ₁ of the core region 110 is 2.7%, the relative refractive index difference Δn ₂ of the first cladding 121 is −0.50%, and the second cladding 122 is based on the third cladding 123. Has a relative refractive index difference Δn ₃ of 0.40%,
The ratio (2a / 2c) of the outer diameter of each of the core region 110 and the second cladding 122 is 0.19, and the ratio of the outer diameter of each of the first cladding 121 and the second cladding 122 (2b / 2).
c) is 0.67. The dispersion compensating optical fiber DCF7 according to the seventh embodiment has an outer diameter 2c of the second cladding 122.
Is 15.2 μm, a wavelength dispersion D _DCF of −215.8 ps / nm / km at a wavelength of 1550 nm,
−2.12 ps / nm ² / km dispersion slope S _DCF , 1
It has an effective area of 3.1 μm ² , a bending loss of 1.3 dB / m and a transmission loss of 0.75 dB / km at a bending diameter of 20 mm. The cutoff wavelength was 1514 nm, and the ratio (S _DCF / D _DCF ) at a wavelength of 1550 nm was 0.0097 / nm.

FIG. 13 is a graph showing the relationship between chromatic dispersion and dispersion slope at a wavelength of 1550 nm of the dispersion compensating optical fibers according to the fifth to seventh embodiments. In FIG. 13, G510 indicates a curve for the fifth embodiment,
G610 shows the curve for the sixth embodiment, and G710
Shows the curve for the seventh embodiment. Here, when the outer diameter 2c of the second cladding 122 is changed, the chromatic dispersion D in the dispersion compensating optical fiber according to each of the embodiments is changed.
The relationship between _DCF and dispersion slope S _DCF is shown. FIG.
As can be seen from the graph of FIG. 3, the dispersion compensating optical fiber DC
In each of F5 to DCF7, the second clad 122
Even if the outer diameter 2c of the laser beam changes, the range of the chromatic dispersion D _DCF is approximately −200 ps / nm / km to −120 ps / nm.
/ Km, the change in the ratio (S _DCF / D _DCF ) is small.
In the dispersion compensation optical fiber DCF5 according to the fifth embodiment, when the outer diameter 2c of the second cladding 122 changes by 2%, the ratio (S _DCF / D _DCF ) changes by 7.7% or less;
Further, the range of the chromatic dispersion D _DCF is -192 ps / n while the variation of the ratio (S _DCF / D _DCF ) is maintained at 10% or less.
m / km to -135 ps / nm / km. In the dispersion compensating optical fiber DCF6 according to the sixth embodiment, the second
When the outer diameter 2c of the cladding 122 changes by 2%, the ratio (S _DCF / D _DCF ) changes by 4.6% or less, and the amount of change of the ratio (S _DCF / D _DCF ) keeps 10% or less. The range of the chromatic dispersion D _DCF is -226 ps / nm / km
−１−146 ps / nm / km. In the dispersion compensating optical fiber DCF7 according to the seventh embodiment, when the outer diameter 2c of the second cladding 122 changes by 2%, the ratio (S _DCF
/ D _DCF ) changes by 4.9% or less, and further the ratio (S _DCF)
/ D _DCF ) is maintained at 10% or less, and the range of the chromatic dispersion D _DCF is −269 ps / nm / km to −1.
73 ps / nm / km. If the change in the ratio (S _DCF / D _DCF ) is suppressed to 10% or less when the outer diameter 2c of the second clad 122 changes by 2%, a dispersion-compensating optical fiber having preferable chromatic dispersion characteristics can be easily manufactured. can do.

FIG. 14 is a graph showing the wavelength dependence of bending loss at a bending diameter of 140 mm for the dispersion compensating optical fibers according to the fifth to seventh embodiments. In FIG.
G520 shows the curve for the fifth embodiment, and G62
0 indicates a curve for the sixth embodiment, and G720 indicates a curve for the seventh embodiment. At this time, the outer diameter 2c of the second cladding 122 of the dispersion compensating optical fiber DCF5 according to the fifth embodiment is 19.4 μm, and the outer diameter 2c of the second cladding 122 of the dispersion compensating optical fiber DCF6 according to the sixth embodiment is 16. 2.0 μm, the outer diameter 2c of the second cladding 122 of the dispersion compensating optical fiber DCF7 according to the seventh embodiment is 1
It was 5.2 μm. As can be seen from the graph of FIG. 14, each of the dispersion compensating optical fibers DCF5 to DCF7 has a small bending loss in a wavelength range of 1610 nm or less.

Therefore, the dispersion compensating optical fiber DCF5
To DCF7 are not only preferably used as the dispersion compensating optical fiber 32 applied as a part of the optical transmission line 30 of the optical transmission system 1 shown in FIG. 1, but also the optical transmission system shown in FIG. 2 is also suitably used as the dispersion compensating optical fiber 32 forming the second dispersion compensating module.
Thereby, chromatic dispersion can be compensated with low loss not only in the C band but also in the L band.

FIG. 15 is a graph showing the wavelength dependence of chromatic dispersion for the dispersion compensating optical fibers according to the fifth to seventh embodiments. Also in FIG. 15, G530 is the fifth
The curve for the embodiment is shown, G630 shows the curve for the sixth embodiment, and G730 shows the curve for the seventh embodiment. Here, the outer diameter 2c of the second cladding 122 of the dispersion compensating optical fiber DCF5 according to the fifth embodiment.
Is 19.4 μm, and the outer diameter 2c of the second cladding 122 of the dispersion compensating optical fiber DCF6 according to the sixth embodiment is 16.0.
μm, dispersion compensating optical fiber DCF7 according to the seventh embodiment
The outer diameter 2c of the second cladding 122 is 15.2 μm.

FIG. 16 shows the dispersion compensating optical fiber according to the fifth to seventh embodiments and the dispersion-shifted optical fiber (4 ps / nm / km chromatic dispersion and 0.046
FIG. 10 is a graph showing the wavelength dependence of the average chromatic dispersion as viewed from the whole for a configuration in which a dispersion slope of ps / nm / km is connected. In FIG. 16, G54
Numeral 0 indicates a curve for a configuration in which the dispersion compensating optical fiber DCF5 according to the fifth embodiment is connected to the dispersion-shifting optical fiber NZDSF of Literature 2, and G640 indicates the dispersion compensating optical fiber DCF6 of the sixth embodiment and Literature 2. G740 shows a curve for a configuration in which the dispersion-shifted optical fiber NZDSF is connected, and G740 indicates the dispersion-compensating optical fiber DCF7 according to the seventh embodiment and the dispersion-shifted optical fiber NZ in Reference 2.
3 shows a curve for a configuration connected to a DSF. 80
In order to compensate for the chromatic dispersion at a wavelength of 1550 nm of the dispersion-shifted optical fiber NZDSF having a length of km, the dispersion-compensating optical fiber DCF5 according to the fifth embodiment includes:
A length of 2 km is required, and the dispersion compensating optical fiber DCF6 according to the sixth embodiment has a length of 1.9 km, and the dispersion compensating optical fiber DCF7 according to the seventh embodiment has a length of 1.7 km.
Length is required.

The dispersion compensating optical fiber D according to the fifth embodiment
In the configuration in which the SF5 and the dispersion-shifted optical fiber NZDSF were connected, the deviation of the average chromatic dispersion as a whole was 0.2 ps / nm / km or less in a wavelength band (C band) of 1535 nm to 1560 nm. In the configuration in which the dispersion compensating optical fiber DSF6 and the dispersion shift optical fiber NZDSF according to the sixth embodiment are connected, 1535n
m to 1600 nm wavelength band (C band and L band)
, The deviation of the average chromatic dispersion from the whole is 0.2p
s / nm / km or less. Further, in the configuration in which the dispersion compensating optical fiber DSF7 and the dispersion-shifting optical fiber NZDSF according to the seventh embodiment are connected, 1535 nm to
In the 1600 nm wavelength band (C band and L band), the deviation of the average chromatic dispersion as a whole is 0.2 ps /
nm / km or less. Therefore, these can perform optical transmission over a relay distance of 400 km at a bit rate of 40 Gb / s.

As shown in FIG. 8, when the dispersion compensating optical fiber DCF5 according to the fifth embodiment having a length of 2.2 km is wound with a bending diameter of 140 mm so as to form a dispersion compensating module, the wavelength at a wavelength of 1550 nm is obtained. The dispersion compensation amount is -640 ps / nm, and the total loss (wavelength 1550 n
m) was 3.0 dB. When the dispersion compensating optical fiber DCF6 according to the sixth embodiment having a length of 1.9 km is wound with a bending diameter of 140 mm to form a dispersion compensating module, the dispersion compensation amount at a wavelength of 1550 nm is -640.
ps / nm and the total loss (wavelength 1550 nm) is 2.
7 dB. Further, when the dispersion compensating optical fiber DCF7 according to the seventh embodiment having a length of 1.7 km is wound with a bending diameter of 140 mm so as to form a dispersion compensating module, the dispersion compensation amount at a wavelength of 1550 nm is -640p.
s / nm and the total loss (wavelength 1550 nm) is 2.5
dB.

The dispersion compensating optical fiber DCF5 according to the fifth embodiment is wound with a bending diameter of 140 mm to form a dispersion compensating module, and has a wavelength of 1550 n.
When the dispersion compensation amount at m was -320 ps / nm, the total loss (wavelength 1550 nm) was 2.0 dB. When the dispersion compensating optical fiber DCF6 according to the sixth embodiment is wound with a bending diameter of 140 mm to form a dispersion compensating module and the dispersion compensation amount at a wavelength of 1550 nm is -320 ps / nm, the total loss (wavelength 1550 nm) was 1.9 dB. Further, the dispersion compensation optical fiber DCF7 according to the seventh embodiment is wound with a bending diameter of 140 mm to form a dispersion compensation module, and the dispersion compensation amount at a wavelength of 1550 nm is-.
When it is 320 ps / nm, the total loss (wavelength 1550n)
m) was 1.7 dB.

As described above, the dispersion compensating optical fiber DCF5
DCF7 can compensate the chromatic dispersion and dispersion slope of the dispersion-shifted optical fiber NZDSF in a short wavelength and a low loss in a wide wavelength band including a wavelength of 1550 nm. (Comparative example)

For comparison with the dispersion compensating optical fibers according to the first to seventh embodiments, a dispersion compensating optical fiber as a comparative example will be described. 17A and 17B are a diagram showing a cross-sectional configuration of a dispersion compensating optical fiber as a comparative example and a refractive index profile thereof. The comparative example 200 includes a core region 210 extending along a predetermined axis and a core region 210.
Is provided with a cladding region 220 provided so as to surround the outer periphery of. The core region 210 has a first refractive index n ₁ and an outer diameter 2a.
Having. Further, the cladding region 220 includes a first cladding 221 having a second refractive index n ₂ (<n ₁ ) and an outer diameter 2b.
And a third cladding 222 having a third refractive index n ₃ (> n ₂ , <n ₃ ) provided so as to surround the outer periphery of the first cladding 221.

Refractive index profile 2 shown in FIG. 17B
50 indicates a refractive index of each part on a line L2 in FIG. 17A,
Regions 251, 252 in the refractive index profile 250,
253 are the core region 210 and the first cladding 22 respectively.
1, the refractive index of each part of the second clad 222 on the line L2.

Comparative Example 20 shown in FIGS. 17A and 17B
0, the relative refractive index difference Δn ₁ of the core region 210 with the second clad 222 as a reference region, the first clad 221
The relative refractive index difference [Delta] n ₂ of each given by the following equations.

[Formula 2] Here, n ₁ is the refractive index of the core region 210, n ₂ is the refractive index of the first cladding 221, and n ₃ is the refractive index of the second cladding 222. In this specification, the relative refractive index difference of each part is expressed as a percentage, and each parameter in the above equation does not change in order. Therefore, the relative refractive index difference of the glass region having a lower refractive index than the second lad 222 (reference region) is represented by a negative value.

In the comparative example 200, the second clad 22
The core region 210 has a refractive index n ₃ of 1.2.
% Relative refractive index difference Δn ₁ , and the first cladding 221
It has a relative refractive index difference Δn ₂ of 0.36%. Further, the ratio Ra (= 2) of the outer diameter of the core region 210 and the first cladding 221.
a / 2b) is 0.5.

FIG. 18 is a graph showing the relationship between chromatic dispersion and dispersion slope at a wavelength of 1550 nm of a dispersion compensating optical fiber as a comparative example. This figure shows the relationship between the chromatic dispersion D _DCF and the dispersion slope S _DCF when the outer diameter 2b of the first cladding 221 changes. In the range where the chromatic dispersion is −40 ps / nm / km or less, this comparative example has poor bending characteristics and cannot be used. When the outer diameter 2c of the second cladding 222 changes, the ratio ( _Sd) of the chromatic dispersion D _DCF to the dispersion slope S _DCF is changed.
_DCF / D _DCF ) greatly changes. For example, when the outer diameter 2b of the first cladding 221 is 10.0 μm, the chromatic dispersion D _DCF is −28 ps / nm / km (a state corresponding to the point A in FIG. 18), and the dispersion slope S _DCF is −0. .
081 ps / nm ₂ / km. When the outer diameter 2b of the first cladding 221 is 9.8 μm, the chromatic dispersion D
_{The DCF} is −22 ps / nm / km (the state corresponding to the point B in FIG. 18), and the dispersion slope S _DCF is −0.0
It is 56 ps / nm ₂ / km. When the outer diameter 2b changes by 2% around this, the ratio (S _DCF / D _DCF ) becomes 1
It changes by 7%. Therefore, it is difficult to manufacture a dispersion compensating optical fiber having desired wavelength dispersion characteristics.

In comparison with the dispersion compensating optical fiber of this comparative example,
The dispersion compensating optical fiber according to the embodiment (the first to seventh embodiments)
(Including the dispersion compensating optical fiber according to the embodiment)
Excellent bending characteristics and chromatic dispersion of -40 ps / nm / k
It can be used in a range of not more than m. Ma
In addition, even if the outer diameter 2c of the second clad changes, the chromatic dispersion D
_DCFIs within a certain range, the chromatic dispersion D_DCFMinutes for
Scatter slope S_DCFRatio (S_DCF/ D_DCF) Small change
No. Therefore, the dispersion compensating optical fiber according to the present invention
Can be easily manufactured to have the desired chromatic dispersion characteristics.
Can be.

[0083]

As described in detail above, the dispersion compensating optical fiber according to the present invention has a wavelength of 1550 nm, which is -40 ps / nm / km or less (more preferably -1 ps / nm / km).
00 ps / nm / km to -40 ps / nm / km, or -250 ps / nm / km to -120 ps / nm /
chromatic dispersion D _DCF of km), 0.005 / nm or more (more preferably from 0.005 / nm~0.15 / nm), the ratio of the dispersion slope S _DCF for the chromatic dispersion D _DCF (S
_DCF / D _DCF ). With such characteristics, the dispersion compensating optical fiber according to the present invention has a wavelength of 15 nm.
In a wide wavelength band including 50 nm, the chromatic dispersion and dispersion slope of the dispersion-shifted optical fiber can be compensated in a short length.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an optical transmission system including an optical transmission line according to the present invention.

FIG. 2 is a diagram showing a schematic configuration of an optical transmission system in which a dispersion-shifted optical fiber is laid on an optical transmission line and a dispersion-compensating optical fiber is arranged in a station as a dispersion-compensating module.

3A is a diagram showing a cross-sectional structure of a dispersion compensating optical fiber according to the present invention, and FIG. 3B is a refractive index profile thereof.

FIG. 4 shows the wavelength 1 of the dispersion compensating optical fiber according to the present invention.
9 is a graph showing the relationship between chromatic dispersion at 550 nm and dispersion slope.

FIG. 5 is a graph showing the wavelength dependence of bending loss at a bending diameter of 140 mm for the dispersion compensating optical fibers according to the first to third embodiments.

FIG. 6 is a graph showing the wavelength dependence of chromatic dispersion of the dispersion compensating optical fibers according to the first to third embodiments.

FIG. 7 is a graph showing the wavelength dependence of the average chromatic dispersion as a whole in each configuration in which one of the dispersion compensating optical fibers and the dispersion-shifted optical fiber according to the first to third embodiments are fusion-spliced to each other. is there.

FIG. 8 is a diagram showing a schematic configuration of a chromatic dispersion module according to the present invention.

FIG. 9 is a graph showing a relationship between chromatic dispersion at a wavelength of 1550 nm and a dispersion slope of the dispersion compensating optical fiber according to the fourth embodiment.

FIG. 10 is a graph showing the wavelength dependence of bending loss at a bending diameter of 140 mm for the dispersion compensating optical fiber according to the fourth embodiment.

FIG. 11 is a graph showing the wavelength dependence of chromatic dispersion in the dispersion compensating optical fiber according to the fourth embodiment.

FIG. 12 is a diagram illustrating the wavelength dependence of the average chromatic dispersion as a whole when the dispersion compensating optical fiber and the dispersion shift optical fiber according to the fourth embodiment are fusion-spliced to each other.

FIG. 13 is a graph showing the relationship between the chromatic dispersion at a wavelength of 1550 nm and the dispersion slope of the dispersion compensating optical fibers according to the fifth to seventh embodiments.

FIG. 14 is a graph showing the wavelength dependence of bending loss at a bending diameter of 140 mm for the dispersion compensating optical fibers according to the fifth to seventh embodiments.

FIG. 15 is a graph showing the wavelength dependence of chromatic dispersion in the dispersion compensating optical fibers according to the fifth to seventh embodiments.

FIG. 16 is a graph showing the wavelength dependence of the average chromatic dispersion as a whole in each configuration in which any of the dispersion compensating optical fibers and the dispersion-shifted optical fibers according to the fifth to seventh embodiments are fusion-spliced to each other. It is.

17A is a diagram showing a cross-sectional structure of a dispersion-compensating optical fiber as a comparative example, and FIG.

FIG. 18 shows wavelength 1 of a dispersion compensating optical fiber as a comparative example.
9 is a graph showing the relationship between chromatic dispersion at 550 nm and dispersion slope.

[Explanation of symbols]

1, 2 optical transmission system, 10, 20 station, 30 optical transmission line, 31 dispersion-shifted optical fiber, 32, 100 dispersion-compensating optical fiber, 110 core region, 120 clad region, 121 first clad , 122 ... second clad,
123: Third clad.

Claims (31)

[Claims] 1. A dispersion-compensating optical fiber having a core region extending along a predetermined axis and a cladding region surrounding the outer periphery of the core region, wherein various characteristics at a wavelength of 1550 nm are -40 ps / nm / km or less. and chromatic dispersion D _DCF, 0.005 / nm is greater than or equal to, the dispersion compensating optical fiber having a ratio of dispersion slope S _DCF for the chromatic dispersion _{D DCF (S DCF / D DCF} ). 2. As various characteristics at a wavelength of 1550 nm, -1
00ps / nm / km or more and -40ps / nm / km
And a wavelength dispersion D _DCF, is 0.005 / nm or more and 0.015 / nm or less, and having a ratio of dispersion slope S _{D CF} for the chromatic dispersion _{D DCF (S DCF / D DCF} ) The dispersion compensating optical fiber according to claim 1. 3. The dispersion-compensating optical fiber according to claim 1, wherein the optical fiber has an effective area of 16 μm ² or more at a wavelength of 1550 nm. 4. The dispersion-compensating optical fiber according to claim 3, wherein the optical fiber has an effective area of 20 μm ² or more at a wavelength of 1550 nm. 5. The dispersion compensating optical fiber according to claim 1, having a cutoff wavelength of 1.2 μm or more and 1.8 μm or less. 6. The dispersion compensating optical fiber according to claim 5, wherein the optical fiber has a cut-off wavelength of 1.4 μm or more and 1.8 μm or less. 7. The method according to claim 1, wherein the wavelength is 0.5 dB /
2. A transmission loss of less than km.
The dispersion compensating optical fiber according to the above. 8. The cladding region has a first refractive index, the cladding region surrounds an outer periphery of the core region, and has a second cladding having a second refractive index lower than the first refractive index. A second layer surrounding the outer periphery of the first cladding and having a third refractive index higher than the second refractive index;
2. The dispersion compensating optical fiber according to claim 1, further comprising a cladding, and a third cladding surrounding a periphery of the second cladding and having a fourth refractive index lower than the third refractive index. 9. The dispersion compensating light according to claim 8, wherein the core region has a relative refractive index difference of 0.8% or more and 2.0% or less based on the third refractive index. fiber. 10. The dispersion compensating light according to claim 9, wherein the core region has a relative refractive index difference of 0.8% or more and 1.5% or less based on the third refractive index. fiber. 11. The dispersion compensating optical fiber according to claim 8, wherein the first cladding has a relative refractive index difference of −0.4% or less based on the third refractive index. 12. The dispersion compensating optical fiber according to claim 8, wherein the ratio (S _DCF / D _DCF ) changes by 10% or less when the outer diameter of the second cladding region changes by 2%. . 13. Various characteristics at a wavelength of 1550 nm include -250 ps / nm / km or more and -120 ps / nm
The chromatic dispersion of not more than nm / km, the ratio of the dispersion slope S _DCF to the chromatic dispersion D _DCF (S _DCF / D _DCF ) of not less than 0.005 / nm, and the effective area of not less than 10 μm ^{2 and not} more than 20 μm ² 2. The dispersion compensating optical fiber according to claim 1, comprising: 14. The ratio of the dispersion slope S _DCF for the chromatic dispersion _{D DCF (S DCF / D DCF} ) , the dispersion compensating optical fiber according to claim 13, wherein a is 0.015 / nm or less. 15. The effective sectional area is (20− | D _DCF)
14. The dispersion compensating optical fiber according to claim 13, wherein the value is in the range of | / 25) or more and (23− | D _DCF | / 25) or less. 16. At a wavelength of 1550 nm, 1.0 dB
14. The dispersion compensating optical fiber according to claim 13, having a transmission loss of not more than / km. 17. The first cladding, wherein the core region has a first refractive index, the cladding region surrounds an outer periphery of the core region, and has a second cladding having a second refractive index lower than the first refractive index. A second layer surrounding the outer periphery of the first cladding and having a third refractive index higher than the second refractive index;
14. The dispersion compensating optical fiber according to claim 13, further comprising a clad, and a third clad surrounding a periphery of the second clad and having a fourth refractive index lower than the third refractive index. 18. The dispersion compensating light according to claim 17, wherein the core region has a relative refractive index difference of 2.0% or more and 3.0% or less based on the third refractive index. fiber. 19. The dispersion compensating optical fiber according to claim 17, wherein the first cladding has a relative refractive index difference of −0.4% or less based on the third refractive index. 20. The dispersion compensating optical fiber according to claim 17, wherein the ratio (S _DCF / D _DCF ) changes by 10% or less when the outer diameter of the second cladding region changes by 2%. . 21. The dispersion compensating optical fiber according to claim 1, which is connected to the dispersion compensating optical fiber and has a wavelength of 1
Various characteristics at 550 nm include +2 ps / nm / k
m and not more than +10 ps / nm / km,
+0.04 ps / nm ² / km or more and +0.12 ps
An optical transmission line provided with a dispersion-shifted optical fiber having a dispersion slope of not more than / nm ² / km. 22. In the wavelength band of 1535 nm or more and 1560 nm, the deviation of the entire average chromatic dispersion is 0.2%.
3. The structure according to claim 2, wherein the speed is not more than ps / nm / km.
2. The optical transmission line according to 1. 23. In the wavelength band of 1535 nm or more and 1600 nm, the deviation of the entire average chromatic dispersion is 0.2%.
3. The structure according to claim 2, wherein the speed is not more than ps / nm / km.
2. The optical transmission line according to 2. 24. A dispersion compensating module including the dispersion compensating optical fiber according to claim 1, wound in a coil shape for modularization. 25. When the dispersion compensation amount at a wavelength of 1550 nm is -640 ps / nm, the total loss is 7 dB in a wavelength band of 1535 nm or more and 1565 nm or less.
The dispersion compensation module according to claim 24, wherein: 26. The dispersion compensation module according to claim 25, wherein the total loss is 7 dB or less in a wavelength band of 1535 nm or more and 1610 nm or less. 27. When the dispersion compensation amount at a wavelength of 1550 nm is −320 ps / nm, the total loss is 3 dB in a wavelength band of 1535 nm or more and 1565 nm or less.
The dispersion compensation module according to claim 24, wherein: 28. The dispersion compensation module according to claim 27, wherein a total loss is 3 dB or less in a wavelength band of 1535 nm or more and 1610 nm or less. 29. It has a core region extending along a predetermined axis, a cladding region surrounding the outer periphery of the core region, and various characteristics at a wavelength of 1550 nm are −40 ps /
wavelength dispersion D _{DCF of not} more than nm / km and 0.005 / nm
The dispersion slope S _{DCF with} respect to the chromatic dispersion D _DCF is described above.
(S _DCF / D _DCF ) ratio and a dispersion compensating optical fiber having an effective area of 16 μm ² or more. 30. The effective sectional area has a wavelength of 1550 nm.
3 has an effective area of 20 μm ² or more.
10. The dispersion compensating optical fiber according to item 9. 31. It has a core region extending along a predetermined axis, a cladding region surrounding the outer periphery of the core region, and various characteristics at a wavelength of 1550 nm are −40 ps /
As the ratio (S _DCF / D _DCF ) of the chromatic dispersion D _DCF of nm / km or less and the dispersion slope S _DCF to the chromatic dispersion D _DCF ,
A ratio of more than 0.005 / nm and 0.5 dB / k
A dispersion compensating optical fiber having a transmission loss of m or less.