JP3997842B2 - Optical transmission system and optical transmission method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical transmission device, an optical transmission system, and an optical transmission method using a Raman amplification function of an optical signal.
[0002]
[Prior art]
In recent years, due to the spread of the Internet and the like, long-distance transmission between continents by submarine optical cables using optical communication lines enabling high-speed and large-capacity has been actively 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, a technique is known 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 an optical signal. In addition, by using the optical transmission line itself as an amplifying medium and inputting excitation light having a wavelength of about 100 nm shorter than the signal light into the transmission line at the same time as the signal light, a physical phenomenon called Raman scattering is caused in the transmission line, and the signal light A Raman amplification technique for directly amplifying the signal is also known (see, for example, Japanese Patent Laid-Open No. 10-022931). In optical amplification by Raman amplification, excitation light is often incident in a direction opposite to the traveling direction of signal light propagating through an optical fiber transmission line.
[0004]
FIG. 4 shows an example of a remote excitation type optical transmission apparatus and optical transmission system using a conventional amplification technique. In this system, transmitters 52a and 52b, EDFs 53a and 53b, optical couplers 54a and 54b, pump light sources 55a and 55b, and receivers 56a and 56b are sequentially arranged from the transmission side with respect to the upstream / downstream main signal paths 51a and 51b. Is arranged. Focusing on the upstream side, the pumping light 58b output from the pumping light source 55a is guided to the main signal path 51a through the optical coupler 54a. First, the above-described Raman amplification is performed in the main signal path 51a up to the EDF 53a. Then, optical amplification using the EDF 53b as an amplification medium (hereinafter referred to as EDF amplification) is performed, and further, Raman amplification is performed by the main signal path 51a to the transmitter 52a. The same applies to descending. As a feature of such a remote excitation type optical amplification technique, it is not necessary to supply electricity to the middle meter, which is more attenuated by transmission than light, and it is not necessary to install an active light source in the repeater. Therefore, it is also effective in terms of maintenance.
[0005]
[Problems to be solved by the invention]
However, in such a conventional remote excitation system configuration, there is a problem that communication is interrupted if this excitation light source goes down due to a sudden accident or the like because there is one excitation light source for remote excitation. It was. In order to solve this problem, there are means to install multiple excitation light sources on the receiving side and remote excitation in both directions by installing an excitation light source on the transmitter side. There was a problem of increasing the cost because it was necessary.
[0006]
An object of the present invention is to provide a remote excitation type optical amplification technique that does not interrupt communication even when the excitation light source suddenly goes down without adding an expensive excitation light source. .
[0007]
[Means for Solving the Problems]
The remote pumping optical amplification technique of the present invention is characterized in that a certain pumping light is supplied not only to one of the upstream / downstream transmission paths but also to both transmission paths. Specifically, the present invention is characterized in that a path through which the excitation light propagates is provided in the middle of the path so that the excitation light is supplied to the other transmission path with respect to the upstream / downstream transmission path. And
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the optical amplification technique of the present invention will be described in detail with reference to the drawings.
[0009]
[First Embodiment]
FIG. 1 shows a first embodiment of the present invention. In the present invention according to the first embodiment, transmitters 3 and 10, WDM couplers 4 and 11, WDM couplers 5 and 12, and EDF 6 are arranged in order from the transmission side with respect to main signal paths 1 and 2 facing upstream and downstream. 13, WDM couplers 7, 14, excitation light sources 8, 15 and receivers 9, 16 are arranged. The WDM coupler 4 and the WDM coupler 12 and the WDM coupler 5 and the WDM coupler 11 are provided with pumping light paths 17 and 18 so that the pumping light propagates, respectively.
[0010]
Next, the operation of the first embodiment having the above configuration will be described. In the main signal path 1, the signal light 30 output from the transmitter 3 passes through the WDM coupler 4 and WDM coupler 5, is inserted into the EDF 6, and then passes through the WDM coupler 7 and is received by the receiver 9. . Similarly, in the opposing main signal path 2, the signal light 31 output from the transmitter 10 passes through the WDM couplers 11 and 12, is inserted into the EDF 13, passes through the WDM coupler 14, and then passes through the receiver 16. Received. The pumping light 32 supplied from the pumping light source 8 to the main signal path 1 via the WDM coupler 7 is inserted into the EDF 6 and then selectively branched by the WDM coupler 5 and passes through the pumping light path 18. The main signal path 2 on the opposite side is inserted through the WDM coupler 11. Similarly, the pumping light 33 supplied from the pumping light source 15 to the main signal path 2 via the WDM coupler 14 is inserted into the EDF 13 and then selectively branched by the WDM coupler 12 and passes through the pumping light path 17. And inserted into the main signal path 1 on the opposite side via the WDM coupler 4. As a result, the signal light 30 is subjected to Raman amplification by the pumping light 33 in the section from the transmitter 3 to the WDM coupler 4, and the section from the WDM coupler 5 to the EDF 6 and the section from the EDF 6 to the WDM coupler 7. Then, Raman amplification is performed by the excitation light 32, and EDF amplification is performed for the section of EDF6. Similarly, the signal light 31 is subjected to Raman amplification by the pumping light 31 in the section from the transmitter 10 to the WDM coupler 11, and the section from the WDM coupler 12 to the EDF 13 and the section from the EDF 13 to the WDM coupler 14. The Raman amplification is performed by the excitation light 33, and the EDF amplification is performed for the section of the EDF 13.
[0011]
Accordingly, focusing on the main signal path 1 in FIG. 1, the signal light 30 output from the transmitter 3 is divided into sections by the excitation light 32 from the excitation light source 8 and the excitation light 33 from the excitation light source 15. Has been. Also in the main signal path 2, the signal light 31 is optically amplified by dividing the section by the excitation light 32 and the excitation light 33. The signal light and the pumping light may have the same wavelength for both upstream and downstream, or the wavelengths may be slightly changed between upstream and downstream.
[0012]
[Second Embodiment]
FIG. 2 shows a second embodiment of the present invention. In addition, about the component which is not changed with 1st Embodiment, it has the same illustration number. The present invention according to the second embodiment has substantially the same configuration as that of the first embodiment, but the direction of the WDM couplers 4 and 11 is changed to the opposite direction as shown in FIG. Yes. As a result, the pump light 34 is inserted into the main signal path 2 on the opposite side of the first embodiment by the WDM coupler 20. Similarly, the pump light 35 is inserted by the WDM coupler 19 on the opposite side to the first embodiment with respect to the main signal path 1. Note that the wavelengths of the signal lights 34 and 35 and the excitation lights 36 and 37 are slightly changed between upstream and downstream.
[0013]
Also in the second embodiment, the same amplification action as in the first embodiment is obtained, and the signal light 34 is subjected to EDF amplification by the excitation light 36 and Raman amplification is performed by both the excitation lights 36 and 37. In addition, the signal light 35 is subjected to EDF amplification by the excitation light 37 and Raman amplification by both the excitation light 36 and 37.
[0014]
[Third Embodiment]
FIG. 3 shows a third embodiment of the present invention. In addition, the same illustration number is used about the component which is not changed with 1st Embodiment. The present invention according to the third embodiment is characterized in that an optical circulator is used instead of the WDM coupler connected to the pumping light path. Thus, the pumping light 40 is inserted by the optical circulator 21 through the pumping light path 23 and into the transmitter 10 side by the optical circulator 22 with respect to the main signal path 2. Similarly, the pumping light 41 is inserted into the transmitter 3 side by the optical circulator 22 through the pumping light path 23 and by the optical circulator 21 with respect to the main signal path 1.
[0015]
Also in the third embodiment, the same amplification action as in the first embodiment is obtained, and the signal light 38 is subjected to EDF amplification with the excitation light 40 and is divided into sections with both the excitation light 40 and 41. Raman amplification is performed, and the signal light 39 is subjected to EDF amplification by the excitation light 41 and is also divided by both the excitation light 40 and 41 and Raman amplification is performed. The signal light and the pumping light may have the same wavelength for both upstream and downstream, or the wavelengths may be slightly changed between upstream and downstream.
[0016]
It should be noted that an isolator may be appropriately installed in front of the transmitter and the excitation light source. As an example of the wavelength, a WDM wavelength of 1550 nm band is used for the signal light, and a wavelength of 1450 nm band is used for the excitation light.
[0017]
【The invention's effect】
As described above, in the remote pumping optical amplification technology of the present invention, in the upstream / downstream transmission path, the light is divided into sections by the pumping light from the pumping light source installed in each, Even when the output of one of the pumping light sources is reduced, the other pumping light source can provide relief such as increasing the output of the pumping light. Furthermore, even when the output of the transmitter is reduced, the range that can be repaired can be expanded because the two pumping light sources can be used for repair. Thus, according to the present invention, it is possible to construct a highly reliable optical transmission system without newly installing an expensive pumping light source.
[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 showing a configuration of a second exemplary embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a third exemplary embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of an optical transmission system using a conventional remote excitation type optical amplification technique.
[Explanation of symbols]
1, 2 Main signal path 3, 10 Transmitter 4, 5, 11, 12 WDM coupler 6, 13 EDF
7, 14 WDM coupler 8, 15 Excitation light source 9, 16 Receiver 17, 18 Excitation light path 21, 22 Optical circulator 23 Excitation light path 30, 31, 34, 35, 38, 39 Signal light 32, 33, 36, 37 40, 41 Excitation light 51 Main signal path 52 Transmitter 53 EDF
54 WDM coupler 55 excitation light source 56 receiver 57 signal light 58 excitation light

Claims (8)

The first optical fiber transmission line is
A first transmitter for outputting a first signal light;
A first main signal path for propagating the output first signal light;
A first excitation light source that supplies first excitation light that performs Raman amplification on the first signal light;
A first receiver for receiving the first signal light,
The second optical fiber transmission line is
A second transmitter for outputting a second signal light,
A second main signal path for propagating the output second signal light;
A second excitation light source for supplying second excitation light for performing Raman amplification on the second signal light;
A second receiver for receiving the second signal light,
Between the first optical fiber transmission line and the second optical fiber transmission line,
First means for extracting the first excitation light from the first optical fiber transmission line;
Second means for supplying the first pumping light to the second optical fiber transmission line;
Third means for extracting the second pumping light from the second optical fiber transmission line;
An optical transmission system comprising: fourth means for supplying the second pumping light to the first optical fiber transmission line. The optical transmission system according to claim 1 , wherein the first to fourth means are optical couplers. The optical transmission system according to claim 2 , wherein the optical coupler is a WDM coupler. The optical coupler of the second means supplies the first pumping light toward the second transmitter, and the optical coupler of the fourth means toward the first transmitter 4. The optical transmission system according to claim 2, wherein pumping light is supplied. The optical transmission system according to claim 1 , wherein the first to fourth means are optical circulators. Said first and fourth means are performed in the same optical circulator, an optical transmission system according to claim 1 or 5 wherein the second and third means is characterized by being performed in the same optical circulator. The optical transmission system according to any of claims 1 to 6 wherein the optical fiber transmission path, characterized in that is provided with a rare earth-doped optical fiber. The first optical fiber transmission line is
A first transmitter for outputting a first signal light;
A first main signal path for propagating the output first signal light;
A first excitation light source that supplies first excitation light that performs Raman amplification on the first signal light;
A first receiver for receiving the first signal light,
The second optical fiber transmission line is
A second transmitter for outputting a second signal light,
A second main signal path for propagating the output second signal light;
A second excitation light source for supplying second excitation light for performing Raman amplification on the second signal light;
A second receiver for receiving the second signal light,
Between the first optical fiber transmission line and the second optical fiber transmission line,
First means for extracting the first excitation light from the first optical fiber transmission line;
Second means for supplying the first pumping light to the second optical fiber transmission line;
Third means for extracting the second pumping light from the second optical fiber transmission line;
And a fourth means for supplying the second pumping light to the first optical fiber transmission line.

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