JP2005026750A - Optical repeater, optical transmission system, and optical amplification method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable efficiently amplifying the signal light in an optical repeater, an optical transmission system, and an optical amplification method thereof. <P>SOLUTION: In the optical repeater, the optical transmission system, and the optical amplification method thereof; a plurality of media for optical amplification are arranged in one optical repeater, and a stimulation light supplying means for supplying the stimulation light to each of them is provided. In this configuration, each stimulation light is supplied in the same direction with respect to the signal light, thereby gradually amplifying the signal light by the plurality of media for optical amplification. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical repeater, an optical transmission system, and an optical amplification method using a technique for directly amplifying signal light, and more particularly to an optical repeater, an optical transmission system, and an optical amplification method for long-distance transmission.
[0002]
[Prior art]
In recent years, due to the spread of the Internet and the like, long-distance transmission between continents using a submarine optical cable using an optical communication line capable of high speed and large capacity has been performed. Along with this, a technique for efficiently extending the transmission distance is required.
[0003]
In order to realize long-distance transmission, it is effective to directly amplify the signal light that is attenuated along with the transmission as it is. As one of them, there is known an optical amplification technique in which an erbium-doped fiber (hereinafter referred to as EDF) is installed in the middle of a transmission line, and pumping light is supplied to directly amplify signal light and extend a transmission distance. Yes.
[0004]
In the ocean optical system, there is an optical amplification technology that installs only the EDF on the submarine repeater installed far away from the transmitting station and the receiving station, installs the excitation light source at the transmitting station and the receiving station, and supplies the excitation light remotely. is there. In this technique, the excitation light source is not installed in the submarine repeater but in the transmitting station and the receiving station. Therefore, it is not necessary to supply power for driving the excitation light source to the submarine repeater installed far away from the transmitting station and the receiving station. Moreover, it is not necessary to mount an excitation light source or a circuit for driving the excitation light source in the submarine repeater. Therefore, there is an advantage that a space for mounting these in the submarine repeater is not required. Further, since the excitation light source is installed at the transmitting station and the receiving station, there is an advantage that maintenance and inspection are easy to perform.
[0005]
6 and 7 show an example of an optical transmission system using a conventional optical amplification technique by remote excitation.
[0006]
In the conventional example shown in FIG. 6, the signal light transmitter 21 is installed at the transmitting station, and the signal light receiver 22 is installed at the receiving station, and these are connected by the signal light path 23. An optical repeater 28 is installed at a position away from the transmitting station, and an EDF 24 is installed therein. Further, a pumping light transmitter 26 is installed at a position away from the optical repeater 28, and an optical coupler 25 is installed in the optical repeater 28, and these are connected by a pumping light path 27. As described above, the pumping light transmitter 26 that supplies the pumping light to the EDF 24 is installed at a location remote from the optical repeater 28.
[0007]
Next, the operation of this conventional optical amplification technique will be described. The signal light 31 output from the signal light transmitter 21 passes through the signal light path 23 and is input to the optical repeater 28 installed remotely. On the other hand, the remote pumping light 32 output from the pumping light transmitter 26 passes through a pumping light path 27 different from the signal light path 23 and is input to the optical repeater 28 that is also set remotely. The remote pumping light 32 is combined with the signal light 31 via the optical coupler 25 installed in the optical repeater 28 and input to the EDF 24. In the EDF 24, the signal light 31 is directly amplified by the remote excitation light 32. Such a conventional example is described in Patent Document 1, for example.
[0008]
FIG. 7 shows another conventional example, and the same components as those in FIG. 6 are denoted by the same reference numerals. In this conventional example, remote pumping light is supplied from the front and rear to the EDF 24 in the optical repeater 29. In the optical repeater 29, optical couplers 25a and 25b are arranged before and after the EDF 24, and pumping light transmitters 26a and 26b are arranged at positions away from the optical repeater 29, and these are connected to the pumping light path 27a. , 27b, respectively. As a result, the EDF 24 is supplied with the remote excitation light 27a from the front and the remote excitation light 27b from the rear.
[0009]
As another conventional example, in the configuration described in Patent Document 2, a pump installed in the transmitting station and the receiving station is provided for each of the amplifier installed on the transmitting station side and the amplifier installed on the receiving station side. A configuration in which excitation light is supplied from a generator using a fiber different from signal light is shown.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 2-310979 [Patent Document 2]
Japanese Patent Laid-Open No. 11-261177
[Problems to be solved by the invention]
However, in the configuration shown in FIG. 6 of the conventional example, there is a problem that it is difficult to obtain a gain necessary for long-distance transmission. The detailed contents are as follows.
[0012]
In the configuration of FIG. 6, even if it is attempted to increase the gain by increasing the power of the pumping light supplied to the EDF, there is a limit to the power that can be efficiently amplified in the EDF. However, the amplification efficiency decreases. Therefore, there arises a problem that a gain corresponding to the supplied power cannot be obtained. This is because the pumping light supply amount per cross section of the EDF is saturated. Therefore, in the configuration of FIG. 6, there is a problem that a sufficient gain cannot be obtained even if the power of the pumping light to be supplied is increased.
[0013]
Next, in the configuration of FIG. 6, even if the length of the EDF is increased to increase the gain of the signal light, the pumping light is attenuated as it is transmitted through the EDF, so that it is extended beyond a certain length. As a result, the power of the excitation light is attenuated, and the signal light cannot be amplified. Further, since the signal light is attenuated as it is transmitted through the EDF, there arises a problem that the power of the signal light is reduced when the power of the excitation light is insufficient. Therefore, in the configuration of FIG. 6, there is a problem that a sufficient gain cannot be obtained even if the length of the EDF is increased. Further, in the configuration of FIG. 6, since the pump light is supplied on one side, the power of the pump light on the opposite side is lowered, and there is a problem that efficient amplification cannot be performed in the EDF.
[0014]
In order to solve this, in the configuration of FIG. 7, excitation light is supplied from both sides of the EDF. However, even in such a configuration, the number of pumping light supply locations is limited to two. In the amplification of signal light by EDF, there are forward excitation in which excitation light is supplied from the input side of signal light and backward excitation in which excitation light is supplied from the output side of signal light. Generally, forward excitation is backward excitation. It is lower noise and the backward excitation is higher power than the forward excitation. Therefore, in such a configuration, there is a problem that noise due to backward excitation occurs. Further, in the L band band of the signal light wavelength band of 1570 to 1602 nm, the signal light is greatly deteriorated due to the generation of noise due to backward excitation, so that there is a problem that such a configuration cannot be obtained.
[0015]
As described above, it is difficult to efficiently amplify signal light with the conventional configuration. In the ocean optical system, increasing the gain of the signal light even slightly in the submarine repeater reduces the necessary number of submarine repeaters and leads to a significant cost reduction. Therefore, it is required to increase the gain of signal light as much as possible in the submarine repeater. Therefore, how to efficiently amplify the submarine repeater is an important issue.
[0016]
[Means for Solving the Problems]
An optical repeater according to the present invention includes a plurality of optical amplification media that are arranged in series and amplify signal light, a plurality of excitation light supply means that individually supply excitation light to the optical amplification media, and an optical amplification medium And a housing for accommodating the excitation light supply means, and the excitation light supply means are alternately arranged with the optical amplification medium, and supplies the excitation light to the optical amplification medium in the same direction as the traveling direction of the signal light. It is characterized by doing.
[0017]
Alternatively, an optical repeater according to the present invention includes a plurality of optical amplification media that are arranged in series and amplify signal light, a plurality of excitation light supply units that individually supply excitation light to the optical amplification medium, and an optical amplification A housing for accommodating the medium for use and the pumping light supply means, a signal light input optical fiber for inputting the signal light to the optical amplification medium, a signal light output optical fiber for outputting the signal light from the optical amplification medium, A pumping light supply optical fiber for supplying pumping light to each of the optical amplification media via the pumping light supply means, and the pumping light supply means are arranged alternately with the optical amplification medium to transmit the pumping light. The optical signal is supplied to the optical amplification medium in the same direction as the traveling direction of the signal light.
[0018]
That is, the configuration of the optical repeater of the present invention can easily increase the number of pumping light supply locations by arranging optical amplification media in multiple stages and providing pumping light supplying means for each of them. Therefore, it is not necessary to concentrate the power of the pumping light only at one place or two places, and the signal light can be amplified to the maximum while keeping the amplification efficiency high for each optical amplifying medium.
[0019]
In addition, the configuration of the optical repeater of the present invention is such that even if the total length of the optical amplifying medium is extended, pumping light is supplied one after another, and the amount of pumping light is maintained as much as necessary. The signal light does not decrease, and the signal light is always amplified.
[0020]
Furthermore, in the configuration of the optical repeater of the present invention, the supply direction of each pumping light is the same as the signal light. In general, forward excitation is less noisy than backward excitation. Therefore, by making each excitation light forward-excited, the generated noise is not amplified and the SN ratio is not deteriorated. Further, the noise generated in the previous stage is not input to the subsequent stage, and the amplification efficiency is not adversely affected. Further, in the subsequent stage, the excitation light is used for amplifying noise, and the increase in the signal light is not reduced by that amount. In particular, in the L band, such a configuration is effective because backward excitation cannot be used due to excessive noise.
[0021]
An optical transmission system according to the present invention includes an optical repeater including a plurality of optical amplification media that are arranged in series and amplify signal light, and excitation light supply means that supplies excitation light to each of the optical amplification media. The pumping light is supplied to each of the optical fiber for signal light input that inputs the signal light to the optical amplification medium, the optical fiber for signal light output that outputs the signal light from the optical amplification medium, and the pumping light supply means An optical fiber for supplying pumping light, a signal light transmitter for transmitting signal light to the optical fiber for signal light input, a signal light receiver for receiving signal light from the optical fiber for signal light output, and an optical fiber for supplying pumping light And a pumping light transmitter for transmitting pumping light to each of the optical amplifiers, and the pumping light supply means are alternately arranged with the optical amplifying medium, and the optical amplifying medium is arranged in the same direction as the traveling direction of the signal light. It is characterized by supplying to.
[0022]
That is, the optical transmission system of the present invention has a configuration similar to that of the optical repeater of the present invention, and the same operation as the optical repeater of the present invention can be obtained.
[0023]
In the optical amplification method of the present invention, the step in which the signal light is input to the excitation light supply unit, the step in which the excitation light is supplied to the excitation light supply unit, and the signal light and the excitation light proceed in the same way by the excitation light supply unit. A step of multiplexing in the direction, a step of supplying the combined signal light and pumping light to the optical amplification medium, and a step of amplifying the signal light by the pumping light in the optical amplification medium; The amplified signal light is output from the optical amplification medium, and the series of steps is repeated a plurality of times and is performed in the same optical repeater.
[0024]
That is, the optical amplification method of the present invention is an optical amplification method having the same characteristics as the optical repeater of the present invention, and the same operation as the optical repeater of the present invention can be obtained.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of an optical repeater, an optical transmission system, and an optical amplification method thereof according to the present invention will be described in detail with reference to the drawings.
[0026]
FIG. 1 shows a first embodiment of the present invention. The optical repeater and optical transmission system according to the first embodiment includes a signal light transmitter 1, a signal light receiver 2, a signal light path 3 connecting them, a signal light transmitter 1, and a signal light receiver 2. It is comprised by the optical repeater 8 installed in the remote place. The optical repeater 8 includes EDFs 4a to 4n and optical couplers 5a to 5n (n is a positive integer). These are connected in multiple stages alternately in the order of the optical coupler and the EDF. The optical coupler 5a is connected to the signal light path 3 on the transmission side, and the EDF 4n is connected to the signal light path 3 on the reception side. In addition, pumping light transmitters 6 a to 6 n (n is a positive integer) for supplying pumping light are installed at a location away from the optical repeater 8 and are provided separately from the signal light path 3. Pumping light is supplied to the optical couplers 5a to 5n by 7a to 7n (n is a positive integer).
[0027]
Next, the operation of this embodiment will be described. The signal light 11 output from the signal light transmitter 1 is input to the signal light path 3. Next, the signal light 11 is transmitted over several tens of kilometers along the signal light path 3 and gradually attenuated, and then reaches the optical repeater 8. Therefore, the signal light 11 is input to the EDF 4a through the optical coupler 5a installed in the optical repeater 8. On the other hand, the pumping light 12a output from the pumping light transmitter 6a is input to the pumping light path 7a. Next, the pumping light 12a is transmitted through the pumping light path 7a by several tens of kilometers or more and gradually attenuated, and then reaches the optical repeater 8 in the same manner. Therefore, the pumping light 12a is input to the EDF 4a via the optical coupler 5a installed in the optical repeater 8. In the EDF 4a, the signal light 11 is amplified by the excitation light 12a. The amplified signal light 11 is then input to the EDF 4b via the optical coupler 5b. On the other hand, the excitation light 12b output from the excitation light source 6b passes through the excitation light path 7b and is input to the EDF 4b via the optical coupler 5b. In the EDF 4b, the signal light 11 is further amplified by the excitation light 12b. In this way, the signal light 11 is amplified one after another by the EDF provided in multiple stages in the optical repeater 8. Finally, the signal light 11 amplified by the EDF 4n obtains sufficient power for long-distance communication and is output from the optical repeater 8. The signal light 11 is received by the signal light receiver 2 after being transmitted through the signal light path 3 from several tens km to several hundreds km or more.
[0028]
Further, the operation of the signal light and the excitation light in each EDF will be described in detail.
The signal light 11 that has been attenuated by the long-distance transmission is in a state where the power is reduced most immediately before being input to the EDF 4a. Next, as the signal light 11 is transmitted through the EDF 4a, it is amplified by the pumping light 12a, and the power is highest at the output end of the EDF 4a. On the other hand, the excitation light 12a is input into the EDF 4a and attenuates as it is transmitted through the EDF 4a, and the power is lowest at the output end of the EDF 4a. Therefore, even if the pumping light 12a is input into the next EDF 4b, it does not have the power to amplify the signal light 11, and if the pumping light is not newly supplied, the signal light 11 is attenuated in the EDF 4b. . Therefore, the signal light 11 is also amplified in the EDF 4b by newly supplying the excitation light 12b to the EDF 4b. As described above, in the first embodiment, the EDF is arranged in multiple stages, and another pumping light is supplied one after another, so that the signal light is not attenuated in the EDF, Amplified. In addition, since each pump light is attenuated by being transmitted through each EDF, even if it is input to the next EDF, it will not be excessively supplied with the next pump light supplied. .
[0029]
The amplification of signal light by EDF includes forward pumping in which pumping light is supplied from the signal light input side and backward pumping in which pumping light is supplied from the signal light output side. Generally, forward excitation has lower noise than backward excitation, and backward excitation has higher power than forward excitation.
[0030]
Therefore, in the first embodiment, the forward excitation is used, so that the noise generated in each EDF can be suppressed low, and no noise is input to the next EDF. Therefore, noise is input to the next EDF and amplified, and the SN ratio does not deteriorate every time it passes through the EDF. In addition, once noise is generated and input to the next EDF, the excitation light is also used for noise amplification. For this reason, in the multi-stage EDF, if the noise at each EDF is kept low as forward excitation rather than backward excitation, the amplification efficiency is not hindered by the next EDF. Output is obtained. In particular, in the L band band of 1570 to 1602 nm, the generation of noise due to backward excitation is large, so such a configuration is effective.
[0031]
In FIG. 1, the pumping light transmitters 6 a to 6 n may be installed at the same place as the signal light transmitter 1 or may be installed at another place. Further, in the optical repeater 8 installed at a position close to the transmission side, pumping light transmitters 6a to 6n are installed on the transmission side as shown in FIG. The pumping light transmitters 6a to 6n are installed on the receiving side. Further, an optical repeater may be installed on each of the transmission side and the reception side, and excitation light may be supplied from each of the transmission side and the reception side.
[0032]
In the case of a marine optical system, the signal light transmitter 1 and the signal light receiver 2 are installed at a land transmission station and a reception station, and the optical repeater 8 is installed on the seabed apart from these. The signal light path 3 is a submarine optical cable and connects them. In the case of a land optical system, the optical repeater 8 is also installed on land, and the signal light path 3 is a land optical cable.
[0033]
FIG. 2 shows typical signal light input / output characteristics when the power of pumping light is constant in an optical amplifier using an EDF. In general, an optical amplifier using EDF has a characteristic that the higher the input power of signal light, the higher the output power of signal light until the input power of the signal light reaches the saturation region indicated by the hatched line in FIG. . Therefore, if the power of the input signal light can be increased until the saturation region is reached, a higher output can be obtained.
[0034]
Therefore, in the first embodiment of the present invention, the pumping light is supplied to the EDFs arranged in multiple stages until the input power of the signal light reaches the saturation region, and the signal light is amplified.
[0035]
Next, in the first embodiment of the present invention, the case where the EDF has two stages will be described in detail. FIG. 3 shows the configuration of the first embodiment of the present invention, FIG. 8 shows the configuration of FIG. 6 which is the conventional embodiment 1, and FIG. 9 shows the configuration of FIG. 7 which is the conventional embodiment 2, respectively. Indicates.
[0036]
In the configuration of the first embodiment of the present invention shown in FIG. 3, a 1.55 μm band light source is used for the signal light transmitter 1, and excitation light sources having different wavelengths in the 1.48 μm band are used for the pump light transmitters 6a and 6b. Wavelength multiplexed ones were used. As an example, the pumping light transmitter 6a uses 1.43 μm and 1.48 μm wavelength-multiplexed, and the pumping light transmitter 6b uses 1.45 μm and 1.50 μm wavelength-multiplexed. The optical fibers of the signal light path 3 and the pumping light paths 7a and 7b are 50 km single-mode optical fibers. The EDFs 4a and 4b have the same characteristics and the same length. In the configuration of the conventional first embodiment shown in FIG. 8, the same signal light transmitter, signal light receiver, and signal light path as in FIG. 3 are used, and only one stage of EDF is installed in this, and the same excitation light as in FIG. A configuration in which forward pumping is performed using one of the transmitter and the pumping light path is used.
[0037]
The configuration of the conventional second embodiment shown in FIG. 9 uses the same signal light transmitter, signal light receiver, and signal light path as those in FIG. 3, and only one EDF is installed in the signal light transmitter. The configuration is such that forward pumping and backward pumping are performed using an optical transmitter and a pumping light path.
[0038]
FIG. 4 shows experimental results in FIG. 3, which is an experimental system of the first embodiment of the present invention, and FIGS. 8 and 9 which are experimental systems of the conventional embodiment 1 and the conventional embodiment 2. In the configuration of the first example of the present invention, +17.0 dBm was obtained in the signal light receiver. On the other hand, in the configurations of the conventional Examples 1 and 2 in which only one EDF is installed, only +14.6 dBm and +15.0 dBm can be obtained in the signal light receiver. As described above, when only one pumping light supply unit is provided as shown in FIG. 8, even when two pumping light supply units are provided as shown in FIG. As in the configuration of the first embodiment, the power of the signal light could not be increased. Thus, in the configuration of the first embodiment of the present invention, it was possible to increase the power of the signal light as compared with the conventional configuration.
[0039]
In addition, although the example which used the pump light source of the same 1.48 micrometer wavelength band was shown for pump light transmitter 6a and 6b, the pump light source of a different wavelength band like a 1.48 micrometer wavelength band and a 0.98 micrometer wavelength band was shown. The pumping light transmitter 6a may use a 1.48 μm band, and the pumping light transmitter 6b may use a pumping light source having different wavelength bands. Moreover, you may use the excitation light source of a single wavelength for each. Moreover, although the example which used the general single mode optical fiber from the surface of cost or maintainability was shown for the excitation light path | route, you may use the multimode optical fiber with a low attenuation factor of excitation light. Further, multistage EDFs having different characteristics and lengths may be used.
[0040]
The signal light may be L-band having a wavelength band of 1.57 to 1.6 μm. In addition, a signal light having a wavelength of 1.4 μm may be used, and thulium doped fiber (TDF) may be used instead of EDF. Alternatively, a praseodymium-doped fiber (PDF) may be used instead of EDF by using a 1.3 μm band for the wavelength of the signal light.
[0041]
FIG. 5 shows the configuration of the second embodiment of the present invention. Parts that are not changed from the first embodiment are assigned the same reference numerals. In the configuration of the second embodiment of the present invention, the EDF 4a to EDF 4n in FIG. 1 are replaced with dispersion compensating fibers (hereinafter referred to as DCF) 10a to 10n (n is a positive integer). In the present technology, the signal light is amplified using the Raman amplification effect instead of using the excitation amplification effect by the EDF. Therefore, in the present technology, the DCF having a smaller core diameter than that of a normal single mode optical fiber is used to increase the power density in the optical fiber and enhance the Raman amplification effect. The signal light and the excitation light are inserted into a DCF having a small core diameter, thereby increasing the power density and producing a higher Raman amplification effect. This is called the concentrated Raman amplification effect. The same effect can be obtained by using a single mode optical fiber having a core diameter of 5 μm or less, which is smaller than that of a general single mode optical fiber, instead of using DCF. A highly nonlinear optical fiber having a small core diameter may be used.
[0042]
Also in the present technology, the signal light 11 is Raman-amplified in each of the DCFs 10 a to 10 n to obtain power necessary for long-distance transmission, and is output from the optical repeater 9. Also in this configuration, each pumping light is attenuated by transmitting each DCF, so even if the next pumping light is supplied, the pumping light is not excessively supplied. Therefore, excessive supply of the pumping light does not cause a nonlinear effect on the signal light in the DCF and does not deteriorate the signal light.
[0043]
【The invention's effect】
As described above, the optical repeater, the optical transmission system, and the optical amplification method thereof according to the present invention include multiple stages of optical amplification media in the optical repeater and includes means for supplying pumping light thereto. Since it is configured, the amount of signal light that can be amplified in one optical repeater can be made larger than in the past. As described above, since the optical amplifying medium is divided and the pumping light is input separately, the amount of pumping light supplied per place is reduced and a large amount of pumping light is supplied to one place. Thus, the amplification efficiency can be prevented from being lowered.
[0044]
Further, since the signal light can be amplified to the maximum with one optical repeater, it is possible to extend the distance to the next required optical repeater. Therefore, the number of expensive optical repeaters required for the system can be reduced.
[0045]
Furthermore, by using forward pumping with respect to the optical amplification media provided in multiple stages, both low noise and high output can be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a first exemplary embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of input / output characteristics of an optical amplifier using an EDF according to the first embodiment of the present invention.
FIG. 3 is a diagram showing an experimental system when the EDF has two stages in the first embodiment of the present invention.
FIG. 4 is a table showing a comparison experiment result of output power.
FIG. 5 is a diagram showing a configuration of a second exemplary embodiment of the present invention.
FIG. 6 is a diagram showing a first example of an optical transmission system using a conventional remote pumping light amplification technique;
FIG. 7 is a diagram showing a second example of an optical transmission system using a conventional remote pumping light amplification technique;
FIG. 8 is a diagram showing an experimental system in Example 1 of a conventional optical transmission system.
FIG. 9 is a diagram showing an experimental system in Example 2 of a conventional optical transmission system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Signal light transmitter 2 Signal light receiver 3 Signal light path | route 4a, 4b-4n EDF
5a, 5b-5n Optical couplers 6a, 6b-6n Pumping light transmitters 7a, 7b-7n Pumping light paths 8, 9 Optical repeaters 10a, 10b-10n DCF
11 Signal light 12a, 12b-12n Excitation light

Claims (24)

A plurality of optical amplification media arranged in series to amplify signal light;
A plurality of excitation light supply means for supplying excitation light to each of the optical amplification media;
A housing for housing the optical amplification medium and the excitation light supply means;
The optical repeater, wherein the pumping light supply means is arranged alternately with the optical amplification medium, and supplies the pumping light to the optical amplification medium in the same direction as the traveling direction of the signal light. . A plurality of optical amplification media arranged in series to amplify signal light;
A plurality of excitation light supply means for supplying excitation light to each of the optical amplification media;
A housing for housing the optical amplification medium and the excitation light supply means;
An optical fiber for signal light input for inputting the signal light to the optical amplification medium;
An optical fiber for signal light output that outputs the signal light from the optical amplification medium;
A pumping light supply optical fiber that supplies the pumping light to each of the optical amplification media via the pumping light supply means;
The optical repeater, wherein the pumping light supply means is arranged alternately with the optical amplification medium, and supplies the pumping light to the optical amplification medium in the same direction as the traveling direction of the signal light. . 3. The optical repeater according to claim 2, wherein the pumping light supply optical fiber is connected to each of the pumping light supply means, and these are separate lines. 3. The optical repeater according to claim 2, wherein the pumping light supply optical fibers are connected to each of the pumping light supply means, and a plurality of them are combined into one line. The optical repeater according to any one of claims 2 to 4, wherein the pumping light supply optical fiber is a single-mode optical fiber. The optical repeater according to any one of claims 2 to 4, wherein the pumping light supply optical fiber is a multimode optical fiber. The optical repeater according to claim 1, wherein the optical amplification medium is an erbium-doped fiber. The optical repeater according to claim 1, wherein the optical amplification medium is a dispersion compensating optical fiber. The optical repeater according to claim 1, wherein the optical amplification medium is a highly nonlinear optical fiber. The optical repeater according to any one of claims 1 to 6, wherein the optical amplification medium is a single mode optical fiber having a core diameter of 5 µm or less. The optical repeater according to any one of claims 1 to 10, wherein the pumping light supply means is an optical coupler. The optical repeater according to any one of claims 1 to 11, wherein the pumping light includes a plurality of pumping lights having different wavelengths. A plurality of optical amplification media arranged in series to amplify signal light;
An optical repeater comprising excitation light supply means for supplying excitation light to each of the optical amplification media;
An optical fiber for signal light input for inputting the signal light to the optical amplification medium;
An optical fiber for signal light output that outputs the signal light from the optical amplification medium;
An excitation light supplying optical fiber for supplying the excitation light to each of the excitation light supplying means;
A signal light transmitter for transmitting the signal light to the signal light input optical fiber;
A signal light receiver for receiving the signal light from the optical fiber for signal light output;
A pumping light transmitter for transmitting the pumping light to each of the pumping light supply optical fibers,
The pumping light supply means is installed alternately with the optical amplifying medium, and supplies the pumping light to the optical amplifying medium in the same direction as the traveling direction of the signal light. . The optical transmission system according to claim 13, wherein the pumping light supply optical fiber is connected to each of the pumping light supply means and is separately taken out from the optical repeater. The pumping light supply optical fiber is connected to each of the pumping light supply means, and a plurality of the pumping light supply optical fibers are combined into one and taken out from the optical repeater as the same path. Item 14. The optical transmission system according to Item 13. The optical transmission system according to claim 13, wherein the pumping light supply optical fiber is a single mode optical fiber. The optical transmission system according to claim 13, wherein the pumping light supply optical fiber is a multimode optical fiber. The optical transmission system according to any one of claims 13 to 17, wherein the optical amplification medium is an erbium-doped fiber. The optical transmission system according to claim 13, wherein the optical amplification medium is a dispersion compensating optical fiber. The optical transmission system according to claim 13, wherein the optical amplification medium is a highly nonlinear optical fiber. 18. The optical transmission system according to claim 13, wherein the optical amplification medium is a single mode optical fiber having a core diameter of 5 μm or less. The optical transmission system according to any one of claims 13 to 21, wherein the pumping light supply means is an optical coupler. The optical transmission system according to any one of claims 13 to 22, wherein the excitation light includes a plurality of excitation lights having different wavelengths. A step in which signal light is input to the excitation light supply means;
A step of supplying excitation light to the excitation light supply means;
The signal light and the excitation light are combined in the same traveling direction by the excitation light supply means;
Supplying the combined signal light and pumping light to an optical amplification medium;
The signal light is amplified by the excitation light in the optical amplification medium;
The amplified signal light is output from the optical amplification medium,
The series of steps is repeated a plurality of times and is performed in the same optical repeater.

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