JPH11326671A - Wavelength multiplex optical transmission path and optical fiber used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wavelength multiplex optical transmission path, which is small in the deviation in the dependence of transmission loss of a wavelength about 1,550 nm band on a wavelength and is capable of compensating the wavelength dispersion of a single-mode optical fiber. SOLUTION: This wavelength multiplex optical transmission path 10 is laid between a light signal transmitter 11 and a light signal receiver 14. The wavelength multiplex optical transmission path 10 is formed by serially connecting the single-mode optical fiber 12 and the dispersion compensation optical fiber 13. Boron is added to at least either of the core and cladding of the dispersion compensation optical fiber 13. The boron-added optical fiber is connected to the single-mode optical fiber 12, by which the dependence of the transmission loss of the wavelength multiplex optical transmission path 10 on the wavelength is lessened, and the deviation of the wavelength loss of the wavelength multiplex optical transmission path 10 becomes capable of planarization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength division multiplexing optical transmission line used for 1.55 .mu.m band optical communication and an optical fiber used for the same.

[0002]

2. Description of the Related Art With the development of the information-oriented society, the amount of communication information tends to increase drastically, and high-speed and large-capacity optical fiber communication has become a necessary and indispensable subject. In recent years, WDM (Wavelength Division Multiplexing) transmission optical communication has been studied as an approach for increasing the speed and capacity in this optical fiber communication. The wavelength division multiplexing transmission system is a system for transmitting a plurality of signal lights having different wavelengths to one optical fiber. With the advent of EDFAs (erbium-doped fiber amplifiers), optical signals can be directly amplified, and it is no longer necessary to convert optical signals into electrical signals for each wavelength, as in the past. Is accelerating.

Further, in order to increase the capacity of an optical communication system, it has been considered to perform high-speed communication in a 1550 nm wavelength band using an existing optical transmission line. However, a single mode optical fiber (1.3 μm zero-dispersion optical fiber) widely laid at present as an optical transmission line has a wavelength of 1 μm.
It has a positive dispersion around 550 nm, and its value is about 1
7 ps / nm / km. For example, when a long distance transmission such as 100 km is performed, a dispersion as large as 1700 ps / nm occurs. Therefore, a dispersion compensating means for compensating the dispersion is required. Therefore, for example, a method of inserting a negative high dispersion fiber (DCF) into an optical transmission line to cancel the positive dispersion of the single mode optical fiber has been considered as a practical dispersion compensation method.

The DCF is formed by making the relative refractive index difference Δ of the core with respect to the cladding high, for example, 1% or more, and reducing the core diameter. Thus, by appropriately setting the refractive index structure of the optical fiber, an optical fiber having a negative dispersion and a large absolute value can be formed. The refractive index distribution structure of DCF is described in, for example, JP-A-6-11620. Such a DCF has, for example, a high refractive index of the core formed by adding a high concentration of germanium (Ge) to the core, and has a structure similar to that of a normal optical fiber except for the refractive index structure. . Therefore, by inserting and connecting a DCF in series with the optical transmission line of the single-mode optical fiber, the chromatic dispersion of the optical transmission line can be compensated, so that the dispersion can be easily compensated.

In order to compensate for the chromatic dispersion of a single mode optical fiber, the DCF has a negative chromatic dispersion.
In addition, an optical fiber having a large absolute value and a DC
By forming F into an optical fiber having a dispersion slope opposite to that of a single mode optical fiber,
This enables dispersion compensation over a wide wavelength range and makes it possible to construct a transmission system suitable for wavelength multiplexing.

[0006]

On the other hand, an optical fiber for wavelength division multiplex transmission is required to have not only dispersion characteristics but also small wavelength dependence of transmission loss characteristics.
A high-concentration Ge-doped core optical fiber proposed as a CF (dispersion compensating optical fiber) has a large Rayleigh scattering coefficient of the optical fiber. Therefore, it is difficult to obtain loss flatness over a wide wavelength band. The high-concentration Ge-doped core optical fiber is susceptible to OH contamination, and the OH contamination causes absorption having a peak near a wavelength of 1.39 μm, which also hinders the realization of the loss flatness. Problem.

Specifically, wavelengths of 1520 nm to 1580, which are 1.55 μm wavelength bands of wavelength division multiplexing transmission optical fibers.
The deviation of the wavelength dependence of the transmission loss in nm is desirably 0.5 dB or less for the entire optical transmission line. Beyond this, in some cases, it is necessary to add an attenuator individually for each wavelength, so that the deviation of the wavelength dependence of the transmission loss, that is, {(maximum loss (dB) −minimum loss (d
Unless the value of (B)) / maximum loss (dB)} × 100 can be suppressed within 5%, it is difficult to use it as it is for wavelength multiplex transmission.

The deviation of the wavelength dependence of the transmission loss of a general single mode optical fiber is 0.01 dB per km.
Or less, and even 0.5 km or less even at 50 km.
The deviation of the wavelength dependence of the transmission loss at 1580 nm is
For example, at 15%, it greatly exceeds 5% which is an allowable value of the deviation of the wavelength dependence of the transmission loss, and it is difficult to apply the optical fiber for wavelength multiplex transmission as it is.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a semiconductor device having a wavelength of 1.55 μm.
The deviation of the wavelength dependence of the transmission loss of the band is small, thereby providing an optical transmission line that enables wavelength multiplex transmission in the wavelength band, and an optical fiber suitably used for the optical transmission line. To provide.

[0010]

In order to achieve the above-mentioned object, the present invention has the following structure to solve the problem. That is, the first invention is used for a wavelength division multiplexed optical transmission line, and compensates for a single mode optical fiber having a zero dispersion wavelength near 1.31 μm and a dispersion characteristic of the single mode optical fiber in a 1.55 μm wavelength band. And a dispersion compensating optical fiber for serially connecting the single mode optical fiber and the dispersion compensating optical fiber, wherein the single mode optical fiber and the dispersion compensating optical fiber are formed by covering a core with a cladding. In order to compensate for the wavelength dependence of the loss characteristic of the optical transmission line or the dispersion compensating optical fiber itself, at least one of the compensating optical fiber and at least one of the core and the cladding is provided with boron. Means to do that.

Further, the second invention is used in a wavelength division multiplexed optical transmission line and has a single mode optical fiber having a zero dispersion wavelength near 1.31 μm, and a dispersion characteristic of the single mode optical fiber in a 1.55 μm wavelength band. An optical transmission line including a line in which a dispersion compensating optical fiber for compensating for the optical fiber is connected in series, wherein the optical transmission line is a light separate from the single mode optical fiber and the dispersion compensating optical fiber. Fibers are connected in series, the separate optical fiber is formed by covering a core with a clad, and in order to compensate for the wavelength dependence of the loss characteristic of the optical transmission line, the separate optical fiber is This is a means for solving the problem with a configuration in which boron is added to at least one of the core and the clad.

Further, a third aspect of the present invention relates to the first or second aspect.
In addition to the configuration of the invention, the optical fiber doped with boron serves as a means for solving the problem with a configuration laid as a line.

Further, a fourth invention is directed to the first or second embodiment.
The optical fiber doped with boron in addition to the structure of the invention described in the above is a means for solving the problem with a structure used as a module.

Further, a fifth invention is an optical fiber for compensating dispersion characteristics of a wavelength division multiplexed optical transmission line, wherein the core of the optical fiber is formed by covering with a clad, and the optical fiber is formed of the optical transmission line. Boron is added to at least one of the core and the cladding to compensate for the wavelength dependence of the loss characteristic of the optical fiber or the optical fiber itself, and the core contains germanium, and the ratio of the maximum refractive index of the core to the cladding is This is a means for solving the problem with a configuration in which the refractive index difference is 0.8% or more.

Further, a sixth aspect of the present invention is a means for solving the problem by providing a configuration in which the chromatic dispersion in the 1.55 μm band is -20 ps / nm / km or less, in addition to the configuration of the fifth aspect.

Further, the seventh invention is directed to the fifth or sixth embodiment.
Wavelength 1520 nm to wavelength 158
The configuration is such that the deviation of the wavelength dependence of the transmission loss at 0 nm is 5% or less, which is a means for solving the problem.

In the present invention having the above structure, boron is added to at least one of the core and the clad of the optical fiber used for at least a part of the wavelength division multiplexing optical transmission line, and the boron has an absorption peak at a wavelength of 2300 nm. If there is boron in the electric field distribution in the optical fiber,
In the wavelength 1550 nm band, the loss is smaller at the shorter wavelength side and larger at the longer wavelength side. Therefore, in the same wavelength band, the loss is larger at the shorter wavelength side due to the influence of Rayleigh scattering and absorption by OH, and the loss is longer at the longer wavelength side. Cancels out the wavelength dependence of the transmission loss of the optical fiber, which makes it possible to flatten the transmission loss of the optical fiber in the same wavelength band, and to reduce the deviation of the wavelength dependence of the transmission loss in the same wavelength band. Becomes possible. Therefore, it is possible to configure an optical transmission line suitable for wavelength multiplex transmission, and the above-mentioned problem is solved.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. The wavelength division multiplexing optical transmission line of this embodiment is configured, for example, as shown in FIG. Here, 10 is a wavelength division multiplexing optical transmission line, and 11 is an optical transmitter (T
X) and 12 are single mode optical fibers, 13 is a dispersion compensating optical fiber, and 14 is an optical receiver (RX). At least one of the single mode optical fiber 12 and the dispersion compensating optical fiber 13 is doped with boron as a dopant. Note that boron is contained in at least one of the core and the cladding, and is added so that the deviation of the wavelength dependence of the transmission loss of the wavelength division multiplexing optical transmission line 10 is reduced.

As an optical fiber to which boron is added, the dispersion compensating optical fiber 13 is more preferable than the single mode optical fiber 12. The reason is that the wavelength dependence of the transmission loss of the dispersion compensating optical fiber 13 is larger than that of the single mode optical fiber 12, so that it is often sufficient to compensate for the wavelength dependence of the transmission loss of the dispersion compensating optical fiber 13. That's why.

A wavelength division multiplexing optical transmission line according to another embodiment of the present invention is configured, for example, as shown in FIG. Here, 20 is a wavelength division multiplexing optical transmission line, 21 is an optical transmitter (T
X) and 22 are single mode optical fibers, 23 is a dispersion compensating optical fiber, 24 is a boron-doped optical fiber, and 25 is an optical receiver (RX). The boron-doped optical fiber 2
Reference numeral 4 denotes that at least one of the core and the clad contains boron, and the amount of boron to be added is determined so that the wavelength-dependent deviation of the transmission loss of the wavelength-division multiplexed optical transmission line 20 is reduced. Further, the configuration shown in FIG. 2 may be obtained by connecting a boron-doped optical fiber in series to the configuration shown in FIG.

The boron-doped optical fiber 24 is, for example, an optical fiber having a zero-dispersion wavelength in the 1.31 μm band.
1. Optical fiber having zero dispersion wavelength in 1.55 μm band;
For example, an optical fiber that compensates for dispersion characteristics in the 55 μm band, such as 1.5
It is desirable that the optical fiber be operated in a single mode in the 5 μm band.

Also, the boron-doped optical fiber, for example, the single mode optical fiber 12, the dispersion compensating optical fiber 13 of FIG. 1, and the boron-doped optical fiber 24 of FIG.
May be laid as a part of the line or may be arranged as a coil-shaped module, but the usage is not limited to these.

Next, with respect to the boron-doped optical fiber of this embodiment, which can be suitably used for the wavelength division multiplexing optical transmission line shown in FIGS. 1 and 2, boron is added to the dispersion compensating optical fiber 13 of FIG. An example will be described. The boron-doped optical fiber (boron-doped optical fiber) of the present embodiment is an optical fiber formed by covering a core around an inner cladding and further covering an inner cladding around an outer cladding. FIG. 3 shows a refractive index distribution structure of a boron-doped optical fiber according to an embodiment of the present invention. As shown in the figure, the boron-doped optical fiber of the present embodiment has a center core 1 (core 5) having a diameter of 2 μm.
m, the diameter of the inner cladding 2 is 7.5 μm, and the refractive index n1 of the center core 1, the refractive index n2 of the inner cladding 2, and the refractive index n3 of the outer cladding 3 satisfy n1>n3> n2. The rate distribution has a W-shaped profile.
The feature of this embodiment is that boron is added to at least one of the center core 1, the inner cladding 2, and the outer cladding 3.

In the boron-doped optical fiber of the embodiment, the outer cladding 3 is formed of pure quartz.
The center core 1 is doped with quartz to increase the refractive index of germanium Ge, and the inner cladding 2 is uniformly doped with fluorine F to reduce the refractive index of the quartz.
The respective addition amounts (doping amounts) of boron B, germanium Ge, and fluorine F are shown in Experiment Nos. 2 to 14 in Table 1. Table 1 shows the amounts of these elements to be added by the values of the relative refractive index differences with respect to pure quartz caused by the addition of the elements. Also, in Experiment No. 1 in Table 1,
For comparison, the composition of the optical fiber formed without adding boron to any of the center core 1, the inner cladding 2, and the outer cladding 3 is shown by the value of the relative refractive index difference with respect to pure quartz.

[0025]

[Table 1]

Experiment Nos. 2 to 7 and Experiment No. 1
In the boron-doped optical fiber according to this embodiment shown in FIGS. 2 to 14, as shown in Table 1 and FIG.
Boron, germanium, and fluorine are added so that the relative refractive index difference Δ− of the inner cladding 2 to the outer cladding 3 becomes approximately −0.55%.

Table 2 shows that each of the optical fibers of Experiment Nos. 1 to 14 has a wavelength band of 1.55 μm (wavelength 15 μm).
20 nm to 1580 nm) at a wavelength interval of 10
The results obtained by examining each nm are shown. Table 2 shows the values of the maximum loss and the minimum loss in the wavelength band, and the deviation value of the wavelength dependence of the transmission loss.

[0028]

[Table 2]

Further, FIGS.
Wavelength 1520 nm to 158 for each of the 11 optical fibers
The results of examining the loss at 0 nm are shown graphically. FIG. 4 shows the data of Experiment Nos. 1 to 3,
FIG. 5 shows the data of Experiment Nos. 1, 4 to 7, and FIG.
Indicates data of experiment numbers 1 and 8 to 11. In addition,
In these figures, the numbers written on the characteristic lines indicate the experiment numbers.

As is clear from these tables and figures,
The boron-doped optical fiber (Experiment Nos. 2 to 14) of the present embodiment formed by adding boron to at least one of the center core 1, the inner cladding 2, and the outer cladding 3 is the same as that of the comparative example shown in Experiment No. 1. The wavelength-dependent deviation of transmission loss in the wavelength band is smaller than that of the optical fiber,
From the viewpoint of the flatness of the wavelength dependence of the loss, it was found that better characteristics were obtained as compared with the optical fiber of the comparative example.

In particular, experiment numbers 2, 5, 9, 12, 13,
When an optical fiber is formed with the composition shown in FIG. 14, the wavelength dependent deviation of the transmission loss in the 1550 nm wavelength band is 5%.
It has been found that very good characteristics can be obtained because the value can be made as small as Further, since light propagating through the optical fiber mainly propagates through the center core 1, if boron is doped into the center core 1 as shown in Experiment Nos. 2 and 3, the wavelength-dependent deviation of the transmission loss due to boron doping is increased. It can be seen that the flattening effect can be exhibited very efficiently. In the case of the present embodiment, 1/10 of the case where boron is added only to the inner cladding 2 and 1/100 of the case where boron is added only to the outer cladding 3. It has been found that the addition amount of 20 can flatten the wavelength-dependent deviation of the transmission loss.

The chromatic dispersion of the boron-doped optical fiber of the present embodiment shown in the above experiment number in the wavelength band of 1550 nm is about -80 ps / nm / km, and the dispersion slope is about -0.27 ps / nm ² /. km, and the chromatic dispersion of the single-mode optical fiber laid for optical transmission in the 1550 nm wavelength band is about 17
ps / nm / km, dispersion slope is about 0.057ps /
nm ² / km, for example, by connecting a boron-doped optical fiber having a length of about ５ with respect to the length of the single mode optical fiber, the chromatic dispersion in the 1550 nm wavelength band of the optical transmission line is obtained. It was also confirmed that could be reduced to almost zero.

According to the present embodiment, as described above, the wavelength loss deviation in the 1550 nm wavelength band can be reduced, so that the existing 1.3 μm zero-dispersion single mode optical fiber can be used in the present embodiment. By inserting the added optical fiber by an appropriate length (for example, / of the 1.3 μm zero dispersion single mode optical fiber),
A system capable of making the chromatic dispersion of the 1.3 μm zero-dispersion single-mode optical fiber substantially zero in the above-mentioned wavelength band and capable of excellent wavelength multiplex transmission without deteriorating loss wavelength flatness can be constructed.

In the embodiment described above, the refractive index distribution structure of the boron-doped optical fiber is a W-type refractive index distribution structure.
The boron-doped optical fiber of the present invention is, for example, as shown in FIG.
As shown in (a), a matched clad type refractive index distribution structure may be used, and as shown in (b) of the same figure, a segmented core type refractive index distribution structure may be used.
In addition, in FIG. 7, 4 has shown the segment layer.

Next, an experimental trial production example of a boron-doped optical fiber having a matched clad type refractive index distribution structure will be described. Table 3 shows the composition of the dopant of the boron-doped optical fiber having the matched clad type refractive index distribution structure by the value of the relative refractive index difference, and Table 4 shows the wavelength of 1550 nm band (wavelength 1520).
-1580 nm) at a wavelength interval of 10 nm.
The data examined for each is shown. Table 4 shows the values of the maximum loss and the minimum loss in the wavelength band, and the deviation value of the wavelength dependence of the transmission loss. 8 and 9
Is a graph showing the relationship between the wavelength and the transmission loss for each of the optical fibers of Experiment Nos. 1 to 7 in Table 4, and the number written on the characteristic line of each graph indicates the experiment number.

In the boron-doped optical fibers of the present embodiment shown in Experiment Nos. 2 to 8, Table 3 and FIG.
(A), the relative refractive index difference Δ + of the center core 1 with respect to pure quartz is approximately 2.4%, and the relative refractive index difference Δ− of the clad 3 with respect to pure quartz is approximately −0.45%. , Boron, germanium, and fluorine are added.

[0037]

[Table 3]

[0038]

[Table 4]

As is apparent from this trial production experiment, the wavelength-dependent deviation of the transmission loss is suppressed to 5% or less by using the boron-doped optical fiber having the dopant composition of Experiment Nos. 2, 5, 6, and 8. Can be. Further, since the light propagating through the optical fiber mainly propagates through the center core 1, as shown in the experimental numbers 2 and 3, the center core 1
It can be understood that when boron is doped, the effect of flattening the wavelength-dependent deviation of the transmission loss due to boron doping can be exhibited very efficiently, and in the case of this embodiment, it is 1/10 of the case where boron is added only to the cladding 3. It was found that the wavelength-dependent deviation of the transmission loss could be flattened by the amount of addition of.

Next, an experimental trial production example of a boron-doped optical fiber having a segmented core type refractive index distribution structure will be described. Table 5 shows the composition of the dopant of the boron-doped optical fiber having the segmented core type refractive index distribution structure by the value of the relative refractive index difference, and Table 6 shows the wavelength of 1550 nm band (wavelength 152
0 nm to 1580 nm) at a wavelength interval of 10 n.
The results of examination for each m are shown. Table 6 shows the values of the maximum loss and the minimum loss in the wavelength band, and the deviation value of the wavelength dependence of the transmission loss. Figure 10
FIG. 13 is a graph showing the relationship between the wavelength and the transmission loss for each optical fiber of Experiment Nos. 1 to 15 in Table 6, and the numbers written on the characteristic lines of each graph indicate the experiment numbers. .

Experiment Nos. 2 to 11 and Experiment No. 1
In the boron-doped optical fiber according to this embodiment shown in FIGS. 6 to 26, as shown in Table 5 and FIG. 7B, the relative refractive index difference Δ + of the center core 1 with respect to the outer cladding 3 is approximately 2.3. %, The relative refractive index difference Δ− of the inner cladding 2 with respect to the outer cladding 3 becomes approximately −0.45%, and the relative refractive index difference Δ + of the segment layer 4 with respect to the outer cladding 3.
Is about 0.6% so that boron, germanium,
Fluorine is added respectively.

[0042]

[Table 5]

[0043]

[Table 6]

As is apparent from this trial production experiment, the configuration of the boron-doped optical fiber having the dopant composition of Experiment Nos. 2, 5, 6, 10, 11, 13, 14, and 16 to 26 makes it possible to obtain the wavelength of the transmission loss. The dependency deviation could be suppressed to 5% or less. Further, since light propagating through the optical fiber mainly propagates through the center core 1, if boron is doped into the center core 1 as shown in Experiment Nos. 2 and 3, the wavelength-dependent deviation of the transmission loss due to boron doping is increased. It can be seen that the flattening effect can be exhibited very efficiently,
In the case of this embodiment, 1/10 when boron is added only to the inner cladding 2, 1/15 when boron is added only to the segment layer 4, and 1/10 when boron is added only to the outer cladding 3. It has been found that the wavelength-dependent deviation of the transmission loss can be flattened with the addition amount of / 20.

The present invention is not limited to the above embodiment, but can take various embodiments. For example, a center core 1 or an inner clad 2 for forming a boron-doped optical fiber
The composition of the outer member 3 and the like is not particularly limited and may be appropriately set. For example, by setting the relative refractive index difference of the maximum refractive index of the core (center core and inner cladding) 5 with respect to the cladding to 0.8%, preferably 1% or more, the boron-doped optical fiber of the present invention has negative dispersion. It becomes possible. By doing so, the positive dispersion of the optical transmission line can be reliably compensated for by inserting and connecting the boron-doped optical fiber of the present invention into the existing optical transmission line. Thus, it is possible to realize an optical transmission system suitable for wavelength multiplexing by realizing the loss flatness over a wide band.

Further, in the above embodiment, for example, FIG.
And the wavelength 1 of the boron-doped optical fiber shown in FIG.
The chromatic dispersion in the 550 nm band is about -80 ps / nm.
/ Km, dispersion slope is about -0.27 ps / nm ² / k
m, but the wavelength of the boron-doped optical fiber is 1550 nm.
The values of the chromatic dispersion and the dispersion slope in the band are not particularly limited, and are set appropriately. For example, the chromatic dispersion in the 1550 nm wavelength band is -20 ps / nm.
/ Km or less, the wavelength 1550 of the existing single mode optical fiber optical transmission line with a very short length
The chromatic dispersion in nm can be compensated.

The present invention is not limited to the above-described embodiments (including experimental prototypes), and various application (deployment) techniques can be applied to the present invention without departing from the spirit of the present invention. Included.

[0048]

According to the present invention, boron is added to at least one of the core and the clad of the optical fiber used for at least a part of the wavelength division multiplexing optical transmission line,
Boron has an absorption peak at a wavelength of 2300 nm, and if boron is present in the electric field distribution in the optical fiber, the wavelength becomes 15 nm.
In the 50 nm band, the loss is smaller at the shorter wavelength side and smaller at the longer wavelength side due to the influence of Rayleigh scattering and absorption by OH. In order to make the loss larger, cancel the loss wavelength dependency of the optical fiber,
The loss in the same wavelength band can be flattened, and the wavelength-dependent deviation of the transmission loss in the same wavelength band can be flattened. Therefore, the boron-doped optical fiber of the present invention can be an optical fiber suitable for wavelength multiplex transmission,
By using a boron-doped optical fiber that compensates for the wavelength dependence of the loss characteristic, it is possible to provide a wavelength division multiplexed optical transmission line having excellent transmission quality.

For example, the core of the optical fiber contains germanium, and the relative refractive index difference of the core with respect to the cladding is set to 1% or more, so that the boron-doped optical fiber of the present invention has a negative dispersion. Accordingly, the boron-doped optical fiber of the present invention can be inserted and connected to an existing optical transmission line to compensate for the positive dispersion of the optical transmission line. In addition, as described above, in order to realize the loss flatness in a wide band required at the time of wavelength multiplexing transmission, it is suitable for wavelength multiplexing using the wavelength multiplexing optical transmission line including the boron-doped optical fiber of the present invention. An optical transmission system can be constructed.

Further, according to the present invention, in which the chromatic dispersion in the 1.55 μm band is -20 ps / nm / km or less,
As described above, by forming the absolute value of the negative chromatic dispersion in the 1.55 μm wavelength band to be large, the existing optical transmission line using the short-length boron-doped optical fiber of the present invention in the 1.55 μm wavelength band is used. Since chromatic dispersion can be compensated, an optical transmission system more suitable for wavelength multiplex transmission can be constructed using the wavelength multiplex optical transmission line including the boron-doped optical fiber of the present invention.

Further, a wavelength of 1520 nm to a wavelength of 1580
According to the present invention, in which the wavelength-dependent deviation of the transmission loss in nm is 5% or less, the boron-doped optical fiber of the present invention can be more reliably set by setting the wavelength-dependent deviation in this wavelength region to a small value within 5%. Can be an optical fiber suitable for wavelength division multiplexing transmission.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of a wavelength division multiplexing optical transmission line according to the present invention.

FIG. 2 is an explanatory diagram of another embodiment of a wavelength division multiplexing optical transmission line according to the present invention.

FIG. 3 is a configuration diagram showing a refractive index distribution structure of one embodiment of a boron-doped optical fiber according to the present invention.

FIG. 4 shows wavelengths of 1520 nm to 158 of the boron-doped optical fiber of the above embodiment formed by adding boron to the core.
6 is a graph showing the loss characteristics at 0 nm together with the loss characteristics of the optical fiber of the comparative example.

FIG. 5 shows a wavelength of 1520 nm of the boron-doped optical fiber of the above embodiment formed by adding boron to the inner cladding.
6 is a graph showing the loss characteristics at 〜1580 nm together with the loss characteristics of the optical fiber of the comparative example.

FIG. 6 shows a wavelength of 1520 nm of the boron-doped optical fiber of the above embodiment formed by adding boron to the outer cladding.
6 is a graph showing the loss characteristics at 〜1580 nm together with the loss characteristics of the optical fiber of the comparative example.

FIG. 7 is an explanatory view showing a refractive index distribution structure of another embodiment of the boron-doped optical fiber according to the present invention.

FIG. 8 shows a wavelength of 1520 nm to 1580 of a boron-doped optical fiber according to the present embodiment, which is formed by adding boron to the core of an optical fiber having a matched clad type refractive index distribution structure.
7 is a graph showing the loss characteristics in nm together with the loss characteristics of the optical fiber of the comparative example.

FIG. 9 shows wavelengths of 1520 nm to 15 nm of the boron-doped optical fiber of the present embodiment formed by adding boron to the clad of an optical fiber having a matched clad type refractive index distribution structure.
8 is a graph showing the loss characteristics at 80 nm together with the loss characteristics of the optical fiber of the comparative example.

FIG. 10 shows a wavelength of 1520 nm to 1580 nm of a boron-doped optical fiber according to the present embodiment in which boron is added to the core of an optical fiber having a segment type refractive index distribution structure.
5 is a graph showing the loss characteristics of the optical fiber of Comparative Example together with the loss characteristics of the optical fiber of the comparative example.

FIG. 11 shows a wavelength of 1520 nm to 15 nm of a boron-doped optical fiber of the present embodiment formed by adding boron to the inner cladding of an optical fiber having a segment type refractive index distribution structure.
8 is a graph showing the loss characteristics at 80 nm together with the loss characteristics of the optical fiber of the comparative example.

FIG. 12 shows a wavelength of 1520 nm to 15 nm of a boron-doped optical fiber according to the present embodiment in which boron is added to a segment layer of an optical fiber having a segment type refractive index distribution structure.
8 is a graph showing the loss characteristics at 80 nm together with the loss characteristics of the optical fiber of the comparative example.

FIG. 13 shows wavelengths of 1520 nm to 15 nm of the boron-doped optical fiber of the present embodiment formed by adding boron to the outer cladding of an optical fiber having a segment type refractive index distribution structure.
8 is a graph showing the loss characteristics at 80 nm together with the loss characteristics of the optical fiber of the comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Center core 2 Inner clad 3 Outer clad 4 Segment layer 5 Core 10, 20 Wavelength multiplexing optical transmission line 12, 22 Single mode optical fiber 13, 23 Dispersion compensating optical fiber 24 Boron-doped optical fiber

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/18

Claims (7)

[Claims] 1. Used in a wavelength division multiplexed optical transmission line, 1.31
An optical transmission line in which a single-mode optical fiber having a zero-dispersion wavelength near μm and a dispersion-compensating optical fiber for compensating the dispersion characteristics of the single-mode optical fiber in a 1.55 μm wavelength band are connected in series. The single mode optical fiber and the dispersion compensating optical fiber are formed by covering a core with a clad, and the optical transmission line or the dispersion compensating optical fiber is provided in at least one of the single mode optical fiber and the dispersion compensating optical fiber. A wavelength division multiplexing optical transmission line characterized in that boron is added to at least one of a core and a clad in order to compensate wavelength dependency of its own loss characteristic. 2. The method according to claim 1, which is used for a wavelength division multiplexed optical transmission line.
Optical transmission including a line in which a single-mode optical fiber having a zero-dispersion wavelength near μm and a dispersion-compensating optical fiber for compensating the dispersion characteristics of the single-mode optical fiber in a 1.55 μm wavelength band are connected in series. The road,
The optical transmission line, the single-mode optical fiber and the dispersion compensating optical fiber and a separate optical fiber is configured to be connected in series, the separate optical fiber is formed by covering a core with a clad, A wavelength multiplexing optical transmission line, wherein boron is added to at least one of a core and a clad of the separate optical fiber in order to compensate for wavelength dependence of a loss characteristic of the optical transmission line. 3. The wavelength division multiplexing optical transmission line according to claim 1, wherein the boron-doped optical fiber is laid as a line. 4. The wavelength division multiplexing optical transmission line according to claim 1, wherein the boron-doped optical fiber is used as a module. 5. An optical fiber for compensating a dispersion characteristic of a wavelength division multiplexing optical transmission line, wherein a core of the optical fiber is formed by covering with a clad, and the optical fiber is the optical transmission line or the optical fiber itself. Boron is added to at least one of the core and the clad in order to compensate for the wavelength dependence of the loss characteristic of germanium, and the core contains germanium, and the relative refractive index difference of the maximum refractive index of the core with respect to the clad is 0. 8
% Or more. 6. The chromatic dispersion in a 1.55 μm band is -20 ps / nm / km or less.
The optical fiber according to claim 5. 7. The optical fiber according to claim 5, wherein the deviation of the wavelength dependence of the transmission loss at a wavelength of 1520 nm to 1580 nm is 5% or less.