JP2003149482A - Dispersion compensating optical fiber, dispersion compensating optical fiber module, optical transmission line, and optical transmission system - Google Patents

Abstract

Dispersion compensating optical fiber capable of compensating for both chromatic dispersion and dispersion slope even in the S-band and not causing an increase in loss even when wound on a small reel, and dispersion A compensating optical fiber module is provided. A ratio b / a of a depressed core radius to a center core radius is set to 3.0 to 4.0, and a ratio c / b of a ring core radius to a depressed core radius is set to 1.
0 to 2.0, the ring core radius c is 12 μm to 18 μm, the relative refractive index difference Δ1 of the center core 1 to the cladding 4 is 1.0% to 1.5%, and the ratio of the depressed core 2 to the cladding 4 is Refractive index difference Δ2 -0.2
% To -0.8%, and the relative refractive index difference Δ3 of the ring core portion 3 with respect to the cladding 4 is set to 0.15% to 0.5% to manufacture a dispersion compensating optical fiber.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a dispersion compensating optical fiber used for dispersion compensation of a 1.3 μm band single mode optical fiber having a chromatic dispersion of around +14 ps / nm / km in the 1.50 μm band, and The present invention relates to a dispersion compensating optical fiber module using a dispersion compensating optical fiber.

[0002]

2. Description of the Related Art With the commercialization of erbium-doped optical fiber amplifiers, optical transmission systems using optical amplifiers such as ultra-long-distance non-regenerative repeaters in the 1.53 to 1.63 μm wavelength band have already been commercialized. There is. Also, with the increase in communication capacity, development of wavelength division multiplexing transmission has been rapidly advanced, and some optical transmission lines have already been commercialized. In the future, it is expected that the number of wavelength division multiplexing will increase further by increasing the bandwidth and narrowing the wavelength interval. In response to this, in the S-band band represented by the wavelength range of 1.46 to 1.53 μm, Raman amplified light and thulium-doped optical fiber amplifier have been recently developed, and an optical transmission system using the S-band band has been developed. It is expected to be put to practical use in the future. At this time, assuming high-speed transmission in the S-band, these optical transmission lines have as small a chromatic dispersion as possible in the transmission band, but have a zero chromatic dispersion in order to suppress nonlinear effects. An optical fiber that does not have to be is desirable. In addition, for wavelength division multiplexing transmission, the C-band (wavelength 1.53 to 1.565μ
m), L-band (wavelength 1.565 to 1.625μ
Similar to the optical transmission in m), the gain difference by the erbium-doped optical fiber amplifier in the wavelength band to be used is as small as possible, the chromatic dispersion is also small to some extent, and further, the difference in the dispersion value between each wavelength is made as small as possible. It is important that the dispersion slope is small.

Further, in the recent long-distance transmission system, the wavelength multiplexing number rapidly increases and the power of the light propagating through the optical fiber rapidly increases. Therefore, the control technique of the nonlinear effect is indispensable. The magnitude of this nonlinear effect is represented by n ₂ / A _eff . Here, n ₂ is the nonlinear refractive index of the optical fiber, and A _eff is the effective area of the optical fiber. In order to reduce the non-linear effect, it is necessary to reduce n ₂ or increase A _eff , but since n ₂ is a value peculiar to the material, it is difficult to greatly reduce it with a silica optical fiber. . Therefore, the current development of nonlinear effect suppression optical fiber
The focus is on increasing A _eff .

At present, 1.3 μm band zero dispersion single mode optical fiber networks are spreading all over the world. When transmission in the 1.55 μm band is performed using this optical fiber network, chromatic dispersion of approximately +17 ps / nm / km occurs in the 1.55 μm band. Therefore, when a signal is transmitted using this optical fiber, 40 Gbps
In high-speed transmission, the residual dispersion limits the transmission line length to about several km. Therefore, in order to compensate for this chromatic dispersion, a dispersion compensating optical fiber has been developed and has already been commercialized. This dispersion-compensating optical fiber has a large negative dispersion in the 1.55 μm band, and by connecting a dispersion-compensating optical fiber with an appropriate length and a transmission optical fiber, a single-mode optical fiber for transmission can be used. Positive dispersion can be offset. Although the residual dispersion hinders high-speed transmission, high-speed communication becomes possible by compensating for the dispersion thus accumulated.

Recently, further wavelength multiplexing has been promoted with the increase in communication capacity. For example, wavelength 1.3μm
In the optical fiber for band transmission, there is a movement to expand the transmission band to the S-band band as well as the C-band band and the L-band band. Even in the S-band, the dispersion-compensating optical fiber in the C-band and the L-band is indispensable for high-speed communication, just as the dispersion-compensating optical fiber is indispensable for high-speed communication. . When dispersion compensation is performed using a dispersion compensating optical fiber having a large negative chromatic dispersion and a positive dispersion slope, it is possible to compensate for one wavelength out of a plurality of wavelengths, but the wavelengths around it. The dispersion compensating effect for is reduced, and the transmission characteristics deteriorate as the wavelength increases.

Therefore, a dispersion-slope-compensating dispersion-compensating optical fiber having a W-type refractive index distribution as shown in FIG. 5 (hereinafter abbreviated as "W-profile dispersion-compensating optical fiber") that can obtain a negative dispersion slope. Is being developed.
In FIG. 5, reference numeral 1 is a central core portion, reference numeral 2 is a depressed core portion, and reference numeral 4 is a clad. In this W-profile dispersion-compensating optical fiber, the relative refractive index difference Δ1 of the central core portion 1 with respect to the cladding 4, the relative refractive index difference Δ2 of the depressed core portion 2 with respect to the cladding 4, and the central core portion 1
The dispersion slope can be completely compensated by adjusting the ratio of the radius a of the compressed core portion 2 to the radius b of the depressed core portion 2. Furthermore, in order to improve the bending loss and the characteristics of the dispersion slope, a dispersion slope compensation type dispersion compensating optical fiber having a W-type refractive index distribution with segments as shown in FIG. 1 has also been developed. The dispersion-slope compensation type dispersion-compensating optical fiber manufactured in this way is either connected to a single-mode optical fiber for transmission by connecting this optical fiber to a single-mode optical fiber for transmission or by receiving an existing optical transmission line. The chromatic dispersion and the dispersion slope are compensated by being inserted as a small module on the transmission side or the transmission side.

[0007]

The dispersion compensating optical fiber is required to have a large absolute value and a negative dispersion value necessary for canceling the chromatic dispersion of the transmission optical fiber with a short length. To be done. A conventional dispersion compensating optical fiber has a large absolute value of chromatic dispersion per unit length.
The core is made thin by using a structure in which the relative refractive index difference of the central core is increased and the relative refractive index difference of the clad around the core is reduced. However, when such a W-shaped profile is used, there is a problem that a non-linear effect is likely to occur because the effective core area is small. For example, up to now, there is an example in which the dispersion slope is compensated by using a W-shaped profile, but the effective core area is not sufficiently expanded to 18.4 μm ² .

Further, in the wavelength range of 1.46 to 1.53 μm, the ratio between the chromatic dispersion of the single mode optical fiber for 1.3 μm and its dispersion slope, that is, dispersion slope /
Chromatic dispersion (hereinafter abbreviated as "RDS") is larger than the values in the C-band and L-band, and the RDS changes greatly even in the wavelength band used, resulting in a high compensation rate over the entire S-band band. It was difficult to get. The present invention has been made to solve such problems, and S-
Even in the band, the absolute value of chromatic dispersion is large, and it is possible to compensate both chromatic dispersion and dispersion slope.
A dispersion-compensating optical fiber that has a larger effective core area and a smaller transmission loss than before, and does not cause an increase in loss even when wound on a small reel for a small module, and a dispersion-compensating optical fiber module using this dispersion-compensating optical fiber. The purpose is to provide.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a core and a clad provided on the outer periphery thereof, and the core has at least a refractive index of the clad. A central core portion having a large refractive index,
The depressed core portion provided on the outer periphery of the central core portion and having a refractive index smaller than that of the clad, and the ring core portion provided on the outer periphery of the depressed core portion and having a refractive index higher than that of the cladding, A part radius of 12 μm to 18 μm, a ratio of the depressed core part radius to the central core part radius of 3.0 to 4.0,
The ratio of the radius of the ring core portion to the radius of the depressed core portion is 1.0 to 2.0, the relative refractive index difference between the central core portion and the cladding is 1.0% to 1.5%, and the relative refractive index difference between the depressed core portion and the cladding is 1.0% to 1.5%. From -0.2%-
0.8%, the relative refractive index difference of the ring core portion with respect to the clad is 0.15% to 0.5%, 1.46 μm to 1.
The wavelength dispersion is in the range of −30 to −70 ps / nm / km and the dispersion slope is in the range of −0.1 to −0.5 ps / nm ² / km at at least one wavelength selected from 53 μm. And a dispersion-compensating optical fiber having a cutoff wavelength capable of substantially propagating a single mode. As a result, both chromatic dispersion and dispersion slope can be compensated for in the S-band, and 40 Gb
It is possible to realize a dispersion-compensating optical fiber that enables high-speed transmission of ps.

According to a second aspect of the present invention, a core and a clad provided on the outer periphery of the core are provided, and the core has a central core portion having a refractive index higher than that of the clad, and the central core portion. A depressed core portion having a refractive index smaller than that of the clad provided on the outer circumference, and a ring core portion having a refractive index greater than that of the clad provided on the outer circumference of the depressed core portion,
The radius of the ring core is 12 to 15 μm, the ratio of the radius of the depressed core to the radius of the central core is 3.0 to 4.0, and the ratio of the radius of the ring core to the radius of the depressed core is 1.1 to 1.5. The relative refractive index difference of the core part is 1.3% to 1.5%, and the relative refractive index difference of the depressed core part to the clad is -0.4%.
To −0.5%, the relative refractive index difference of the ring core portion with respect to the cladding is 0.15% to 0.4%, and 1.46 μ
The wavelength dispersion is in the range of −35 to −65 ps / nm / km and the dispersion slope is −0.1 to −0.3 ps / nm at at least one wavelength selected from m to 1.53 μm.
A dispersion-compensating optical fiber having a cutoff wavelength in the range of ² / km and capable of substantially propagating a single mode. This makes it possible to compensate for both chromatic dispersion and dispersion slope in the S-band,
It is possible to realize a dispersion compensating optical fiber that enables high-speed transmission of 40 Gbps.

According to a third aspect of the present invention, in the dispersion compensating optical fiber according to the first or second aspect, the transmission loss is 0.5d.
B / km or less, the longest wavelength of the wavelength band selected from 1.46 μm to 1.53 μm, and the bending loss characteristic at a bending diameter of 20 mm is 100 dB / m or less. Thus, even if the dispersion compensating optical fiber module is formed by winding it on a small reel to form a small module, the loss can be reduced. Claim 4
The described invention is the dispersion compensating optical fiber according to claim 1 or 2, wherein the transmission loss is 0.5 dB / km or less,
The longest wavelength in the wavelength band selected from 1.46 μm to 1.53 μm, the bending loss characteristic at a bending diameter of 20 mm is 20.
It is characterized in that it is not more than dB / m. Thus, even if the dispersion compensating optical fiber module is formed by winding it on a small reel to form a small module, the loss can be reduced.

According to a fifth aspect of the present invention, in the dispersion compensating optical fiber according to any one of the first to fourth aspects, the dispersion slope compensation rate in the wavelength band of 1.50 μm is 70% to 70%.
It is characterized by being 130%. This enables RDS
It is possible to sufficiently compensate for the dispersion slope of the single mode optical fiber in the S-band band having a large value. Claim 6
According to another aspect of the invention, an optical module is formed using the dispersion compensating optical fiber according to any one of claims 1 to 5, and a transmission optical fiber having a positive wavelength dispersion and a positive dispersion slope is dispersed. It is a dispersion compensating optical fiber module characterized by compensation. A seventh aspect of the present invention is an optical transmission system in which the dispersion compensating optical fiber module according to the sixth aspect is inserted into a transmission section or a reception section of an optical signal. According to an eighth aspect of the present invention, the dispersion compensating optical fiber according to any one of the first to fifth aspects is formed into a cable and connected to a transmission optical fiber, and has a positive chromatic dispersion and a positive dispersion slope. An optical transmission line is characterized in that the transmission optical fiber is dispersion-compensated. The invention according to claim 9 is the optical transmission system characterized in that the optical transmission line according to claim 8 is connected between a transmitting section and a receiving section of an optical signal.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
First, a first example of the dispersion compensating optical fiber of the present invention will be described. FIG. 1 shows an example of the refractive index distribution of the first example of the dispersion compensating optical fiber of the present invention. In FIG. 1, reference numeral 1
Is a central core portion, reference numeral 2 is a depressed core portion provided on the outer periphery of the central core portion 1, reference numeral 3 is a ring core portion provided on the outer periphery of the depressed core portion 2, and reference numeral 4 is provided on the outer periphery of the ring core portion 3. It is a clad. The central core portion 1 has a refractive index higher than that of the cladding 4, the depressed core portion 2 has a refractive index lower than that of the cladding 4, and the ring core portion 3 has a refractive index higher than that of the cladding 4. Have a rate. The refractive index distribution of the dispersion compensating optical fiber is set to the W type profile with a segment shown in FIG. 1 because it is possible to satisfy the necessary dispersion characteristics while keeping the value of the effective core cross-sectional area large to some extent. In this example, as shown in FIG. 1, when the radius of the central core portion 1 is a, the radius of the depressed core portion 2 is b, and the radius of the ring core portion 3 is c, the ratio of the depressed core radius to the central core radius is b / a. Is 3.0 to 4.0, and the ratio of the ring core radius to the depressed core radius c
/ B is 1.0 to 2.0, and the ring core radius c is 1
This dispersion compensating optical fiber is formed so as to have a thickness of 2 μm to 18 μm.

The relative refractive index difference Δ1 of the central core portion 1 with respect to the cladding 4 is 1.0% to 1.5%, and the relative refractive index difference Δ2 of the depressed core portion 2 with respect to the cladding 4 is -0.2.
% To -0.8%, the ring core part 3 with respect to the clad 4
The relative refractive index difference Δ3 is 0.15% to 0.5%. This dispersion compensating optical fiber is 1.46 μm to 1.53 μm
Has a chromatic dispersion in the range of −30 to −70 ps / nm / km and a dispersion slope in the range of −0.1 to −0.5 ps / nm ² / km at least one or more wavelengths selected from Yes, and has a cutoff wavelength that allows substantially single mode propagation.

Next, the second dispersion compensating optical fiber of the present invention will be described.
An example will be described. The refractive index distribution of the dispersion compensating optical fiber of this example is also as shown in FIG. 1, but the core diameter and the relative refractive index difference are different from those in the first example. As shown in FIG. 1, when the radius of the central core portion 1 is a, the radius of the depressed core portion 2 is b, and the radius of the ring core portion 3 is c, the ratio b / a of the depressed core radius to the central core radius is 3.0. The dispersion compensating optical fiber is formed so that the ratio of the ring core radius to the depressed core radius is 4.0, the ratio c / b is 1.1 to 1.5, and the ring core radius c is 12 μm to 15 μm. The relative refractive index difference Δ1 of the central core portion 1 with respect to the cladding 4 is 1.3% to 1.5%, and the relative refractive index difference Δ2 of the depressed core portion 2 with respect to the cladding 4 is −0.4% to −0.5%. , Clad 4
Relative refractive index difference Δ3 of the ring core portion 3 with respect to 0.15%
To 0.4%. This dispersion compensating optical fiber is 1.
The wavelength dispersion is −35 to −65 ps / nm / at least at one or more wavelengths selected from 46 μm to 1.53 μm.
It is in the range of km and the dispersion slope is -0.1 to -0.3.
It is in the range of ps / nm ² / km, and has a cutoff wavelength capable of substantially single mode propagation.

Since the optical fibers having the refractive index distributions described in the first and second examples have a negative chromatic dispersion and a negative dispersion slope in the used wavelength band, they have a positive chromatic dispersion and a positive dispersion slope. Can be used as a dispersion compensating optical fiber for dispersion compensation. According to the dispersion compensating optical fiber of this example, the transmission loss is 0.5 dB / km or less, and 1.46 μm to 1.53
The longest wavelength in the wavelength range selected from μm, and the bending diameter is 2
The bending loss characteristic at 0 mm can be 100 dB / m or less, preferably 20 dB / m or less. Moreover, when dispersion-compensating an optical fiber for transmission having a positive wavelength dispersion and a positive dispersion slope, the dispersion slope compensation rate in the wavelength 1.50 μm band can be set within the range of 70% to 130%. Here, the dispersion slope compensation ratio is the ratio of the dispersion slope of the dispersion-compensating optical fiber to the dispersion slope of the transmission single-mode optical fiber, and the ratio of the dispersion value of the dispersion-compensating optical fiber to the dispersion value of the transmission single-mode optical fiber. It is divided by.

A dispersion-compensating optical fiber module is formed by using the above-mentioned dispersion-compensating optical fiber, and the module is inserted as a small module on the receiving side or the transmitting side of the existing optical transmission line to obtain the wavelength dispersion of the transmitting optical fiber. And the dispersion slope can be compensated. Since the dispersion compensating optical fiber of the present invention has a small bending loss characteristic, the loss can be reduced even if the dispersion compensating optical fiber module is formed by winding the dispersion compensating optical fiber module on a small reel to form a small module. It is possible to reduce the size of the fiber module. Further, the above-mentioned dispersion compensating optical fiber itself is made into a cable for an optical transmission line and connected to the transmission optical fiber to form an optical transmission line, so that the chromatic dispersion and dispersion slope of the transmission optical fiber can be compensated. .

FIG. 2 shows an optical transmission system using an optical transmission line constructed by forming the above-mentioned dispersion compensating optical fiber into a cable. In FIG. 2, reference numeral 11 is a transmission optical fiber, and a dispersion compensation optical fiber 12 is connected to the transmission optical fiber 11 to form an optical transmission line.
The optical transmission system is formed by connecting the transmitter 13 and the receiver 14 to the optical transmission line. In the optical transmission system of this example, when optical transmission is performed, positive chromatic dispersion is generated by the transmission optical fiber 11 having a positive chromatic dispersion and a positive dispersion slope, but the dispersion compensating light connected to the optical transmission line is generated. Since the fiber 12 has a negative chromatic dispersion and a negative dispersion slope, the positive chromatic dispersion generated by the transmission optical fiber 11 is compensated by the dispersion compensating optical fiber 12. As another example of the optical transmission system using the dispersion compensating optical fiber, the dispersion compensating optical fiber module can be inserted into the transmitter 13 or the receiver 14 to configure the optical transmission system. In this case, a dispersion-compensated optical transmission system can be realized using an existing optical transmission line.

Specific examples will be shown below. (Example) A W-type dispersion compensating optical fiber with a segment having the refractive index profile shown in FIG. 1 was produced by a known method such as the VAD method, the MCVD method, the PCVD method, or the like. In these dispersion compensating optical fibers, the relative refractive index difference Δ1 of the central core portion 1, the relative refractive index difference Δ2 of the depressed core portion 2, the relative refractive index difference Δ3 of the ring core portion 3, the ratio of the depressed core portion radius to the central core portion radius b / Table 1 shows the ratio c / b of the radius of the ring core to the radius of the depressed core.

[0020]

[Table 1]

Optical characteristics of a dispersion compensating optical fiber having such a refractive index distribution and optical characteristics of a 1.3 μm band transmission single mode optical fiber having a positive chromatic dispersion and a positive dispersion slope to be dispersion-compensated. Is shown in Table 2. Note that the measured values shown in Table 2 are the results measured by making light with a wavelength of 1500 nm incident.

[0022]

[Table 2]

The transmission loss of this dispersion compensating optical fiber is 0.
The low loss of 285 dB enables long-distance transmission. Moreover, since the effective area is as large as 16 μm ² or more,
Even in an optical transmission system in which the wavelength multiplexing number increases and the optical power increases, it is possible to suppress the non-linear effect and to construct an optical transmission system having a large transmission capacity. The bending loss at a bending diameter of 20 mm is 4.19 dB / m.
Since the size of the dispersion compensating optical fiber module is small, the loss can be reduced even if the dispersion compensating optical fiber module is formed by winding it on a small reel to form a small module, and thus the dispersion compensating optical fiber module can be miniaturized. .

The absolute value of chromatic dispersion is -59.2 ps / n.
m / km, dispersion slope is -0.264 ps / nm ² / k
m, which are both negative and have a large absolute value. Therefore, it is possible to effectively perform dispersion compensation on a transmission single-mode optical fiber having a positive chromatic dispersion and a positive dispersion slope. Further, the RDS of the transmission single-mode optical fiber in the S-band band is larger than the RDS in the C-band band and the L-band band, and the wavelength of 15
Although it is 0.0045 nm ⁻¹ for the light of 00 nm, the RDS of the dispersion compensating optical fiber of this embodiment is 0.0045 n.
Since it is m ⁻¹ , the dispersion slope can be sufficiently compensated.

FIG. 3 shows its optical characteristics in Table 2.
The chromatic dispersion in the S-band of the single mode optical fiber for 1.3 μm band transmission and the dispersion compensating optical fiber is shown. Further, FIG. 4 shows the result of dispersion compensation of the single mode optical fiber for 1.3 μm band transmission by the dispersion compensation optical fiber of the present embodiment. The 1.3 μm band single mode optical fiber used for transmission has an optical fiber length of 88 km and the dispersion compensating optical fiber has an optical fiber length of 20 km. According to this example, the dispersion slope compensation rate was close to 100%, and a good result was obtained. As a result, 1.3μ
The residual dispersion in the composite optical transmission line 100 km of the m-band single-mode optical fiber and the dispersion compensating optical fiber for S-band of this embodiment is 50 ps / nm at the maximum, and high-speed transmission of 40 Gbps in the S-band is also possible. Is possible.

[0026]

As described above, according to the present invention,
A central core portion, which includes a core and a clad provided on the outer periphery thereof, and has a refractive index higher than that of the clad, and a refractive index smaller than the refractive index of the clad provided on the outer periphery of the central core portion. And a ring core portion provided on the outer periphery of the depressed core portion and having a refractive index higher than that of the clad, and the radius of the ring core portion is 12 μm to 18 μm.
m, the ratio of the radius of the depressed core portion to the radius of the central core portion is 3.0 to 4.0, the ratio of the radius of the ring core portion to the radius of the depressed core portion is 1.0 to 2.0, and the relative refractive index of the central core portion to the cladding is The difference is 1.0% to 1.
5%, the relative refractive index difference of the depressed core portion with respect to the clad is −0.2% to −0.8%, and the relative refractive index difference of the ring core portion with respect to the clad is 0.15% to 0.5%. By forming an optical fiber having
The wavelength dispersion is −30 to −70 ps / at least at one or more wavelengths selected from 1.46 μm to 1.53 μm.
Within the range of nm / km, dispersion slope is -0.1-
Since it is in the range of 0.5 ps / nm ² / km and has a cut-off wavelength capable of substantially propagating a single mode, it is possible to compensate both chromatic dispersion and dispersion slope in the S-band, and 40 Gbps It is possible to realize a dispersion-compensating optical fiber that enables high-speed transmission.

Further, a central core portion having a core and a clad provided on the outer periphery thereof, wherein the core has a refractive index at least larger than that of the clad, and a refractive index of the clad provided on the outer periphery of the central core portion. The depressed core portion having a refractive index smaller than the refractive index and the ring core portion provided on the outer periphery of the depressed core portion and having a refractive index larger than the refractive index of the cladding have a radius of 1
2 μm to 15 μm, the ratio of the depressed core portion radius to the central core portion radius is 3.0 to 4.0, and the ratio of the ring core portion radius to the depressed core portion radius is 1.1 to 1.
5, the relative refractive index difference of the central core portion with respect to the clad is 1.3% to 1.5%, the relative refractive index difference of the depressed core portion with respect to the clad is −0.4% to −0.5%, and the ring core with respect to the clad. By forming an optical fiber having a refractive index distribution in which the relative refractive index difference between the parts is 0.15% to 0.4%, the wavelength at at least one wavelength selected from 1.46 μm to 1.53 μm is increased. Variance is -3
5 to -65 ps / nm / km, dispersion slope is -0.1 to -0.3 ps / nm ² / km, and has a cut-off wavelength capable of substantially single mode propagation. Therefore, both chromatic dispersion and dispersion slope can be compensated for in the S-band, and a dispersion compensating optical fiber that enables high-speed transmission of 40 Gbps can be realized.

According to the present invention, the wavelength is 1.50 μm.
Since the dispersion slope compensation rate in the band can be set to 70% to 130%, the dispersion slope of the single mode optical fiber in the S-band band having a large RDS can be sufficiently compensated. Further, according to the present invention, the effective area can be increased to 16 μm ² or more, and the nonlinear effect can be suppressed even in the optical transmission system in which the wavelength multiplexing number increases and the optical power increases. It is possible to realize a dispersion compensating optical fiber capable of constructing an optical transmission system with a large size. Further, according to the present invention, the transmission loss is set to 0.5 dB / km or less and 1.4
The longest wavelength in the wavelength band selected from 6 μm to 1.53 μm, and the bending loss characteristic at a bending diameter of 20 mm is 100 dB.
/ M or less, and preferably 20 dB / m or less, so that even if a dispersion compensating optical fiber module is formed by winding it on a small reel to form a small module, the loss can be reduced, resulting in low loss. A dispersion compensating optical fiber module that can be miniaturized can be realized.

According to the present invention, a dispersion compensating optical fiber is formed into a cable and connected to a transmission optical fiber to form an optical transmission line, whereby a transmission optical fiber having a positive wavelength dispersion and a positive dispersion slope is obtained. An optical transmission line capable of dispersion compensation can be realized. Further, according to the present invention, the dispersion compensating optical fiber module is inserted into the transmitting section or the receiving section of the optical signal, or an optical transmission line formed by connecting the cabled dispersion compensating optical fiber to the transmission optical fiber is used as the transmitting section. The optical transmission system capable of high-speed transmission can be realized by being connected between the receiver and the receiver.

[Brief description of drawings]

FIG. 1 is a diagram showing a refractive index distribution of a dispersion compensating optical fiber of the present invention.

FIG. 2 is a diagram showing an example of an optical transmission system of the present invention.

FIG. 3 is a diagram showing chromatic dispersion of a single mode optical fiber for 1.3 μm band transmission and a dispersion compensating optical fiber.

FIG. 4 is a graph of 1 when dispersion-compensating a single-mode optical fiber for 1.3 μm band transmission with the dispersion-compensating optical fiber of the present invention.
It is a figure which shows the chromatic dispersion per km.

FIG. 5 is a diagram showing an example of a refractive index distribution of a conventional dispersion compensating optical fiber.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Central core part, 2 ... Depressed core part, 3 ... Ring core part, 4 ... Clad, 11 ... Transmission optical fiber, 12 ...
Dispersion compensating optical fiber, 13 ... Transmitting unit, 14 ... Receiving unit.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuhiko Aikawa             Fuji Co., Ltd. 1440 Rokuzaki, Sakura City, Chiba Prefecture             Kura Sakura Office (72) Inventor Shinichi Nakayama             Fuji Co., Ltd. 1440 Rokuzaki, Sakura City, Chiba Prefecture             Kura Sakura Office (72) Inventor Kuniharu Himeno             Fuji Co., Ltd. 1440 Rokuzaki, Sakura City, Chiba Prefecture             Kura Sakura Office F-term (reference) 2H050 AB03Z AC14 AC38 AC73                       AD01 AD16

Claims (9)

[Claims] 1. A core comprising a core and a clad provided on the outer periphery thereof, the core having a refractive index at least higher than that of the clad, and a clad provided on the outer periphery of the central core part. Consisting of a depressed core portion having a refractive index smaller than that of, and a ring core portion provided on the outer periphery of the depressed core portion and having a refractive index larger than that of the clad, the radius of the ring core portion is 12 μm to 18 μm, and the radius of the central core portion is The ratio of the radius of the depressed core to 3.0 is 4.0 to 4.0, the ratio of the radius of the ring core to the radius of the depressed core is 1.0 to 2.0, and the relative refractive index difference of the central core to the cladding is 1.0%. To 1.5%, the relative refractive index difference of the depressed core portion relative to the cladding is -0.2% to -0.8%, and the ring core relative to the cladding is The relative refractive index difference in the part (a) is 0.15% to 0.5%, and the chromatic dispersion is −30 to −70 ps / at least at one or more wavelengths selected from 1.46 μm to 1.53 μm.
Within the range of nm / km, dispersion slope is -0.1-
A dispersion compensating optical fiber having a cut-off wavelength capable of substantially single mode propagation in a range of 0.5 ps / nm ² / km. 2. A core and a clad provided on the outer periphery thereof, the core having a refractive index at least larger than that of the clad, and a clad provided on the outer periphery of the central core part. Consisting of a depressed core portion having a smaller refractive index than that of the core, and a ring core portion provided on the outer periphery of the depressed core portion and having a refractive index larger than that of the clad. The radius of the ring core portion is 12 μm to 15 μm, and the radius of the central core portion is The ratio of the radius of the depressed core to 3.0 to 4.0, the ratio of the radius of the ring core to the radius of the depressed core is 1.1 to 1.5, and the relative refractive index difference of the central core to the cladding is 1.3%. To 1.5%, the relative refractive index difference of the depressed core portion relative to the cladding is -0.4% to -0.5%, and the ring core relative to the cladding is The relative refractive index difference in the part A is 0.15% to 0.4%, and the chromatic dispersion is −35 to −65 ps / at least at one or more wavelengths selected from 1.46 μm to 1.53 μm.
Within the range of nm / km, dispersion slope is -0.1-
A dispersion compensating optical fiber having a cutoff wavelength capable of substantially single mode propagation in a range of 0.3 ps / nm ² / km. 3. The transmission loss is 0.5 dB / km or less, the longest wavelength of the wavelength band selected from 1.46 μm to 1.53 μm, and the bending loss characteristic at a bending diameter of 20 mm is 100 dB / m or less. The dispersion compensating optical fiber according to claim 1, wherein the dispersion compensating optical fiber is present. 4. The transmission loss is 0.5 dB / km or less, the longest wavelength of the wavelength band selected from 1.46 μm to 1.53 μm, and the bending loss characteristic at a bending diameter of 20 mm is 20 dB / m or less. The dispersion compensating optical fiber according to claim 1, wherein the dispersion compensating optical fiber is present. 5. The dispersion compensating optical fiber according to claim 1, wherein a dispersion slope compensation rate in a wavelength band of 1.50 μm is 70% to 130%. 6. An optical module is formed using the dispersion compensating optical fiber according to claim 1, and a transmission optical fiber having a positive wavelength dispersion and a positive dispersion slope is dispersed. A dispersion compensating optical fiber module characterized by compensation. 7. An optical transmission system, characterized in that the dispersion compensating optical fiber module according to claim 6 is inserted in a transmitting section or a receiving section of an optical signal. 8. The dispersion compensating optical fiber according to claim 1, which is connected to a transmission optical fiber by forming a cable, and has the positive chromatic dispersion and the positive dispersion slope. An optical transmission line characterized by dispersion compensating an optical fiber. 9. An optical transmission system, wherein the optical transmission line according to claim 8 is connected between a transmission section and a reception section of an optical signal.