JP6965954B2 - Optical repeaters, optical communication systems, and optical communication methods - Google Patents

Description

The present invention relates to an optical repeater, an optical communication system, and an optical communication method, and more particularly to an optical repeater, an optical communication system, and an optical communication method used in an optical submarine relay system.

The optical submarine relay system transmits digital data by relaying signal light transmitted from a transmission device provided in a land base station using an optical repeater and receiving it in a transmission device provided in an opposite land base station. do. The optical submarine relay system includes an optical fiber that propagates signal light that carries data, and an optical repeater that relays the signal light. The optical repeater is installed in the path of the optical fiber, and the attenuated signal light is amplified by an optical amplifier and retransmitted.

An example of such an optical submarine relay system is described in Patent Document 1. FIG. 9A schematically shows the configuration of the related optical seafloor relay system described in Patent Document 1. The related optical submarine relay system 5000 is composed of opposite land stations 5001 and 5002, optical fibers 5100, and optical repeater 5200, respectively, in which transmission devices are installed. In the figure, the land station 5001 and the land station 5002 are connected via n optical repeaters 5200 including an optical repeater 1, an optical repeater 2, ..., an optical repeater n-1, and an optical repeater n. The case where the two optical fiber paths 5101 and 5102 are connected is shown. Here, the optical fiber route 5101 is a route (UP side route) from the land station 5001 to the land station 5002. Further, the optical fiber route 5102 is a route (DOWN side route) from the land station 5002 to the land station 5001.

FIG. 10 shows the configuration of each associated optical repeater 500 included in the optical repeater 5200. The optical repeater 500 includes erbium-doped fibers 511 and 512, a plurality of pump lasers 520, a drive circuit 530 for driving the pump lasers, and a plurality of optical components (not shown).

Here, the erbium-doped fibers 511 and 512 directly amplify the signal light transmitted in the optical seafloor relay system. The plurality of pump lasers 520 excite the erbium-doped fibers 511 and 512 with pump light to generate an optical amplification action. That is, the erbium-doped fiber 511, 512 and the pump laser 520 constitute an erbium-loaded fiber amplifier (EDFA). The optical component includes a signal light, a pump light, a 3 dB coupler that combines and demultiplexes the pump light, and the like.

As shown in FIG. 10, the pump light output by the two pump lasers 520 is combined and demultiplexed by a 3 dB coupler or the like. Then, the erbium-doped fiber 511 of the UP side path (optical fiber path 5101) and the erbium-doped fiber 512 of the DOWN side path (optical fiber path 5102) are excited by each pump light (excitation light).

Here, the reason why the pump laser 520 has a plurality of redundant configurations is that the reliability of the laser element (Laser Diode: LD) constituting the pump laser 520 is relatively low. With the redundant configuration, even if a part of the laser element fails, the influence on the signal light transmission quality can be within an acceptable range in the design of the system. That is, with such a configuration, even if one of the two laser elements fails, the excitation power of the erbium-doped fibers 511 and 512 does not become completely zero, and optical communication is cut off. Can be prevented. As described above, in the related optical seafloor relay system 5000, the excitation light source included in each optical repeater 500 is made redundant by two laser elements. FIG. 9B shows a redundant configuration of the related optical submarine relay system 5000.

International Publication No. 2008/068842

In the related optical seafloor relay system 5000 shown in FIG. 9A, consider a case where one of the excitation laser elements (LD) provided in the optical repeater 2 fails and the excitation light output becomes zero. In this case, the optical communication is not completely cut off, but the optical output of the optical repeater 2 is reduced.

At this time, in the UP side path (optical fiber path 5101), the output of the UP side path of the optical repeater 2 is reduced, so that the input of the UP side path of the optical repeater 3 is reduced. However, the erbium-added fiber amplifier (EDFA) provided in the optical repeater usually has an operating point in a saturation region where the optical output power does not fluctuate much even if the optical input power fluctuates. The output of the UP side route does not fluctuate much. Therefore, the optical repeater located in the subsequent stage from the optical repeater 3 is not affected by the failure of the optical repeater 2. Here, the self-healing effect means that by operating the optical amplifier provided in the optical repeater in the saturation region, even if the input power of the optical amplifier in the first stage is slightly reduced, after passing through some optical repeaters, The effect of returning the output power of the optical repeater to the rated value.

Similarly, for the DOWN side path (optical fiber path 5102), the output of the DOWN side path of the optical repeater 1 does not fluctuate so much, and the influence of the failure of the optical repeater 2 does not reach the land station 5001.

Next, consider the case where one of the excitation laser elements (LD) included in the optical repeater 1 fails. In this case, as in the case described above, the UP side path is not affected by the failure of the optical repeater 1 on the optical repeater located in the subsequent stage from the optical repeater 2. On the other hand, in the DOWN side path, since the optical repeater 1 is the final stage optical repeater in the DOWN side path, the above-mentioned self-healing effect cannot be obtained. Therefore, the optical input power to the land station 5001 is reduced, which affects the communication quality.

As described above, in the related optical relay system, there is a problem that the communication quality deteriorates when the output of the excitation light source included in the optical repeater located at the final stage of the optical communication path decreases.

An object of the present invention is that in a related optical relay system, which is the above-mentioned problem, communication quality deteriorates when the output of an excitation light source included in an optical repeater located at the final stage of an optical communication path decreases. An object of the present invention is to provide an optical repeater, an optical communication system, and an optical communication method that solve the problems.

The optical repeater of the present invention provides excitation light to an input interface that receives an optical signal transmitted from a transmitting station via a first optical fiber, an optical amplification means that amplifies the received optical signal, and an optical amplification means. It is provided with an excitation means for output and an output interface for outputting an amplified optical signal to an external optical repeater via a second optical fiber, and the amplification factor of the optical amplification means is possessed by the external optical repeater. It is characterized in that it is larger than the amplification factor of the optical amplification means.

The optical communication system of the present invention includes a transmitting station that outputs an optical signal to a first optical fiber and a first optical repeater that amplifies an optical signal from the first optical fiber, and is a first relay. The instrument uses an input interface that receives an optical signal from the first optical fiber, an optical amplification means that amplifies the received optical signal, an excitation means that outputs excitation light to the optical amplification means, and an amplified optical signal. It has an output interface that outputs to a second optical repeater via a second optical fiber, and the amplification factor of the optical amplification means is larger than the amplification factor of the optical amplification means of the second optical repeater. It is characterized by that.

The optical communication method of the present invention is used for a step of receiving an optical signal transmitted from a transmitting station via a first optical fiber, a step of optically amplifying the received optical signal, and an optical amplification of the optical signal. Amplification rate, which is a ratio of photoamplifying the received optical signal, including a step of outputting excitation light and a step of outputting an photoamplified optical signal to an external optical repeater via a second optical fiber. Is larger than the amplification factor of the optical signal received by the external optical repeater.

According to the optical repeater, the optical communication system, and the optical communication method of the present invention, even when the output of the excitation light source provided in the optical repeater located at the final stage of the optical communication path is reduced, the communication quality is improved. Deterioration can be suppressed.

It is a block diagram which shows the structure of the optical relay system which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the optical relay system which concerns on 2nd Embodiment of this invention. It is a figure which shows the redundant configuration of the optical relay system which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the optical relay station which concerns on 2nd Embodiment of this invention. It is a figure which shows the redundant configuration of the optical relay system which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the structure of the optical relay station which concerns on 3rd Embodiment of this invention. It is a figure which shows the excitation light power injected into the EDFA provided in the optical relay station which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the structure of the optical relay station which concerns on 4th Embodiment of this invention. It is a figure which shows the excitation light power injected into the EDFA provided in the optical relay station which concerns on 4th Embodiment of this invention. It is a schematic diagram which shows the structure of the related optical seafloor relay system. It is a figure which shows the redundant configuration of the related optical seafloor relay system. It is a block diagram which shows the structure of the related optical repeater.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of an optical relay system 100 according to a first embodiment of the present invention. The optical relay system 100 according to the present embodiment includes an optical communication path 110 configured to transmit signal light from a transmitting station 1001 to a receiving station 1002, and a plurality of optical communication paths 110 located at a plurality of locations. It has an optical repeater 120. The optical communication path 110 is typically composed of an optical fiber.

Each optical repeater included in the plurality of optical repeaters 120 includes an optical amplifier configured to amplify the signal light and an excitation laser configured to excite the optical amplifier. Optical amplifiers typically include erbium-added optical fibers.

Here, the plurality of optical repeaters 120 include a first optical repeater 121 connected to the receiving station 1002, a second optical repeater 122 connected to the transmitting station 1001, and a first optical repeater 121. A third optical repeater 123 located between the and the second optical repeater 122 is included. The number of excitation lasers included in the first optical repeater 121 is larger than the number of excitation lasers included in the third optical repeater 123.

The signal light that waveguides through the optical communication path 110 from the transmitting station 1001 to the receiving station 1002 passes through the first optical repeater 121 connected to the receiving station 1002 and then does not pass through another optical repeater. Reach the receiving station 1002. Therefore, the above-mentioned self-healing effect cannot be obtained.

Here, in the optical relay system 100 according to the present embodiment, the number of excitation lasers included in the first optical repeater 121 is larger than the number of excitation lasers included in the third optical repeater 123. That is, among the plurality of optical repeaters 120, the redundancy of the excitation laser for the optical amplifier of the first optical repeater 121 directly connected to the receiving station 1002 is made higher than the redundancy in the third optical repeater 123. It has a structure.

With such a configuration, according to the optical relay system 100 of the present embodiment, the excitation laser (excitation light source) included in the optical repeater (first optical repeater 121) located at the final stage of the optical communication path. ), The deterioration of communication quality can be suppressed even when the output is reduced.

The number of excitation lasers included in the second optical repeater 122 connected to the transmission station 1001 is the number of excitation lasers included in the first optical repeater 121 and the number of excitation lasers included in the third optical repeater 123. The configuration can be equal to any of the numbers.

Next, the optical relay method according to the present embodiment will be described.

In the optical relay method of the present embodiment, the signal light is amplified at a plurality of optical communication paths that transmit the signal light from the transmitting station to the receiving station. These plurality of locations include a first point adjacent to the receiving station, a second point adjacent to the transmitting station, and a third point located between the first point and the second point. Is done. Then, the magnitude of the optical power for amplifying the signal light at the first point is made larger than the magnitude of the optical power for amplifying the signal light at the third point.

As described above, according to the optical relay system 100 and the optical relay method of the present embodiment, even when the output of the excitation light source included in the optical repeater located at the final stage of the optical communication path is reduced, the output is reduced. Deterioration of communication quality can be suppressed.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 2A is a block diagram showing a configuration of the optical relay system 2000 according to the present embodiment.

The optical relay system 2000 according to the present embodiment has an optical communication path 2100 configured to transmit signal light from a transmitting station to a receiving station, and a plurality of optical relays located at a plurality of locations in the optical communication path 2100. It has a station 2200.

The transmitting station includes a first transmitting station provided in the first base station 2001 and a second transmitting station provided in the second base station 2002. Further, the receiving station includes a first receiving station provided in the first base station 2001 and a second receiving station provided in the second base station 2002.

The optical communication path 2100 is a first optical communication path 2101 configured to transmit signal light from a first transmitting station to a second receiving station, and a second transmitting station to a first receiving station. It includes a second optical communication path 2102 configured to waveguide signal light. That is, the first optical communication path 2101 is a route (UP side route) from the first base station 2001 to the second base station 2002. The second optical communication path 2102 is a path (DOWN side route) from the second base station 2002 to the first base station 2001. The optical communication path 2100 is typically composed of an optical fiber.

The plurality of optical relay stations 2200 include a first relay station and a second relay station. The first relay station is a first optical repeater connected to a first receiving station (first base station 2001) and a first relay station connected to a first transmitting station (first base station 2001). It is equipped with two optical repeaters. The second relay station is a first optical repeater connected to a second receiving station (second base station 2002) and a second relay station connected to a second transmitting station (second base station 2002). It is equipped with two optical repeaters. In FIG. 2A, the first base station 2001 and the second base station 2002 are composed of n units including an optical relay station 1, an optical relay station 2, ..., an optical relay station n-1, and an optical relay station n. The case where the first optical communication path 2101 and the second optical communication path 2102 are connected via the optical relay station 2200 is shown. In this case, the optical relay station 1 is the first relay station, and the optical relay station n is the second relay station.

The first relay station (optical relay station 1) and the second relay station (optical relay station n) are configured to excite the first optical amplifier, the second optical amplifier, and each optical amplifier, respectively. It is equipped with an excitation laser. Each optical amplifier typically comprises an erbium-added optical fiber. The first optical amplifier is configured to amplify the signal light propagating in the first optical communication path 2101 (UP side path). Further, the second optical amplifier is configured to amplify the signal light propagating in the second optical communication path 2102 (DOWN side path).

Here, in the optical relay system 2000 according to the present embodiment, the number of excitation lasers included in the first optical repeater is a third located between the first optical repeater and the second optical repeater. The configuration is larger than the number of excitation lasers provided in the optical repeater of. That is, among the plurality of optical relay stations 2200, the redundancy of the excitation laser for the optical amplifier in the optical relay station 1 and the optical relay station n directly connected to the first base station 2001 and the second base station 2002 is set to the third. The configuration is such that the redundancy is higher than that of other optical relay stations equipped with the optical relay.

FIG. 2B shows a redundant configuration of the optical relay system 2000 according to the present embodiment. In the figure, the number of redundancy is set to "4" only in the optical relay station 1 and the optical relay station n connected to the first base station 2001 and the second base station 2002, and the other optical relay stations 2, 3 and ..., In n-1, an example in which the relay number is set to "2" is shown. As described above, in the optical relay system 2000 according to the present embodiment, the configuration includes those having different redundant numbers of excitation lasers in the plurality of optical relay stations 2200. On the other hand, the related optical submarine relay system 5000 shown in FIG. 9B is different from the optical relay system 2000 according to the present embodiment in that the number of redundant excitation lasers in each optical repeater is the same.

FIG. 3 shows the configuration of the optical relay station 1 and the optical relay station 200 as the optical relay station n.

The optical relay station 200 has an EDFA (Erbium-Doped Fiber Amplifier) 211 as an optical amplifier in the first optical communication path 2101 (UP side path) and an optical amplifier in the second optical communication path 2102 (DOWN side path). EDFA212 is provided. And, as the excitation laser of EDFA211 and EDFA212, four laser elements (Laser Diode: LD) 221, 222, 223, 224 are used.

Here, the output light of the laser element 221 and the output light of the laser element 222 are combined by the polarization synthesis coupler 231 and the output light of the laser element 223 and the output light of the laser element 224 are combined by the polarization synthesis coupler 232. Later, it was configured to combine waves with a 3 dB coupler 240. With such a configuration, it is possible to reduce the amount of decrease in the output light for exciting the optical amplifier when one laser element fails. The reason for this is as follows. That is, in the case where the optical amplifiers of the first optical communication path 2101 and the second optical communication path 2102 are excited, respectively, without passing through the 3dB coupler 240 after the waves are combined by the polarization synthesis couplers 231 and 232. If one laser element fails, the output light will be halved. On the other hand, when the output light is further combined and demultiplexed by the 3 dB coupler 240 as in the optical relay station 200 of the present embodiment, the output light becomes 3/4 and the amount of decrease can be reduced. ..

One output light demultiplexed by the 3 dB coupler 240 is inserted into the EDFA211 by a WDM (Wavelength Division Multiplexing) coupler 251. Similarly, the other output light demultiplexed by the 3 dB coupler 240 is inserted into the EDFA 212 by the WDM coupler 252. As described above, the optical relay station 200 of the present embodiment excites the number of laser elements (excitation lasers) configured to excite the EDFA211 (first optical amplifier) and the EDFA212 (second optical amplifier). The number of laser elements (excitation lasers) configured to do so is the same.

As shown in FIG. 3, the optical relay station 200 according to the present embodiment may further include isolators 261 and 262, 263, 264, and optical filters 271 and 272.

As described above, the optical relay system 2000 of the present embodiment has a configuration in which the number of redundant excitation lasers is increased in the optical relay station 1 and the optical relay station n (optical relay station 200) in which the self-healing effect cannot be obtained. It is supposed to be. With such a configuration, even if the excitation laser fails in the optical relay station 1 and the optical relay station n, the influence of the failure can be reduced. That is, according to the optical relay system 2000 of the present embodiment, deterioration of communication quality is suppressed even when the output of the excitation light source included in the optical repeater located at the final stage of the optical communication path is reduced. Can be done.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.

The block configuration of the optical relay system according to the present embodiment is the same as the block configuration of the optical relay system 2000 according to the second embodiment shown in FIG. 2A. The optical relay system according to the present embodiment and the optical relay system 2000 according to the second embodiment have different redundant configurations of optical relay stations. FIG. 4 shows a redundant configuration of the optical relay system according to the present embodiment.

In the optical relay system 2000 according to the second embodiment, as shown in FIG. 2B, the number of redundant excitation lasers in the optical relay station 1 and the optical relay station n is the first optical communication path 2101 (UP side path). And the second optical communication path 2102 (DOWN side path) has the same configuration.

On the other hand, in the optical relay system according to the present embodiment, as shown in FIG. 4, the redundant number of excitation lasers in the relay station 1 and the optical relay station n is configured to be different between the UP side path and the DOWN side path. Specifically, in the optical relay station 1, the number of redundant excitation lasers is increased only in the DOWN side path (second optical communication path), and in the optical relay station n, the UP side path (first optical communication path). The configuration is such that the number of redundant excitation lasers is increased only in.
That is, in the optical relay station 1 (first relay station), the number of excitation lasers configured to excite the optical amplifier (second optical amplifier) in the DOWN side path is the number of the optical amplifier (second optical amplifier) in the UP side path. The configuration was larger than the number of excitation lasers configured to excite (1 optical amplifier). Further, in the optical relay station n (second relay station), the number of excitation lasers configured to excite the optical amplifier (first optical amplifier) on the UP side path is the number of optical amplifiers (first optical amplifier) on the DOWN side path. The configuration was larger than the number of excitation lasers configured to excite (2 optical amplifiers).

FIG. 5 shows the configuration of the optical relay station 300 as the optical relay station n.

The optical relay station 300 is configured to excite the EDFA211 of the first optical communication path 2101 (UP side path) and the EDFA212 of the second optical communication path 2102 (DOWN side path), and the laser element 321 and the laser element 322. To be equipped with. In addition to this, the optical relay station 300 is provided with a laser element 323 that excites only the EDFA211 of the first optical communication path 2101 (UP side path) from the rear via the WDM coupler 351. With such a configuration, the redundant number of the excitation laser is set to "3" only in the UP side path.

The configuration of the optical relay station 1 is the first optical communication path 2101 (UP side path) and the second optical communication path 2102 (DOWN side path) in the configuration of the optical relay station 300 as the optical relay station n described above. ) Can be replaced to form a similar configuration.

As described above, in the optical relay system according to the present embodiment, the redundant number of excitation lasers is set only in the DOWN side path of the optical relay station 1 where the self-healing effect cannot be obtained and the UP side path of the optical relay station n. It has an increased configuration. Therefore, the number of excitation lasers can be minimized. That is, according to the optical relay system of the present embodiment, the device configuration of the optical relay station can be simplified and the cost can be reduced. Further, as in the case of the optical relay system 2000 according to the second embodiment described above, even if the output of the excitation light source provided in the optical repeater located at the final stage of the optical communication path is reduced, the communication quality is deteriorated. Can be suppressed.

Next, the operation of the optical relay station 300 will be described. In FIG. 5, the numbers described in the vicinity of the laser elements 321-23, 3 dB coupler 240, and WDM coupler 252 indicate the relative optical power of the excitation light at the same location.

FIG. 6 shows the excitation light power injected into the EDFA211 and EDFA212 at the optical relay station 300. In the figure, the optical relay station 300 is in a normal operating state, that is, the laser elements 321 to 323 (LD1 to LD3) are all in a non-failed state, and one of the LD1 to LD3 is in a failed state and the optical output is output. The relative values of the excitation light power when is zero are shown.

Under normal operating conditions, it is assumed that LD1, LD2, and LD3 emit light with optical powers of "1", "1", and "0.5", respectively. In this case, the excitation light of the optical powers "1.5" and "1", which is the sum of the outputs of the LD1 to LD3, is injected into the EDFA211 and the EDFA212, respectively. That is, in the optical relay station 300 as the optical relay station n (second relay station), the magnitude of the optical power for exciting the EDFA211 (first optical amplifier) during the operation of the excitation lasers (LD1 to LD3) is large. , EDFA212 (second optical amplifier) is configured to be larger than the magnitude of the optical power to excite. On the contrary, in the optical relay station 1 (first relay station), the magnitude of the optical power for exciting the EDFA212 (second optical amplifier) during the operation of the excitation laser is determined by the EDFA211 (first relay station). It is configured to be larger than the magnitude of the optical power that excites the optical amplifier (1).

On the other hand, when any one of LD1, LD2, and LD3 fails, the excitation light power to the EDFA211 drops to "1". Further, the excitation light power to the EDFA212 drops to "0.5" when any one of LD1 and LD2 fails. Since the laser element 323 (LD3) is not connected to the EDFA212, the presence or absence of failure of the laser element 323 (LD3) does not affect the excitation light power of the EDFA212.

As can be seen from FIG. 6, even if any of the laser elements (LD) of the laser elements 321 to 323 (LD1 to LD3) fails, the amount of decrease in the excitation light power with respect to the EDFA211 and the EDFA212 is the same. Specifically, in the example shown in FIG. 6, the excitation light powers injected into the EDFA211 and the EDFA212 in the normal operating state are "1.5" and "1", respectively. On the other hand, even if any of the laser elements of LD1 to LD3 fails, the excitation light powers for EDFA211 and EDFA212 are "1" and "0.5", respectively, and the amount of decrease in the excitation light power is both. "0.5" is equal.

Further, as described above, the optical relay station 300 has a configuration in which the number of redundancy of the excitation laser with respect to the EDFA 211 is larger than the number of redundancy of the excitation laser with respect to the EDFA 212. Therefore, when the laser elements (LD1 to LD3) fail, the rate at which the excitation light power for the UP side path where the self-healing effect cannot be obtained decreases (1/3) is the rate at which the excitation light power for the EDFA 212 decreases. It is smaller than (1/2). As a result, it is possible to reduce the influence of the failure of the laser element on the optical relay system without increasing the optical output of the unfailed laser element when the laser element fails.

As described above, in the optical relay system according to the present embodiment, the redundant number of excitation lasers is set only in the DOWN side path of the optical relay station 1 where the self-healing effect cannot be obtained and the UP side path of the optical relay station n. It has an increased configuration. Therefore, the number of excitation lasers can be minimized. That is, according to the optical relay system of the present embodiment, the device configuration of the optical relay station can be simplified and the cost can be reduced. Further, as in the case of the optical relay system 2000 according to the second embodiment described above, even if the output of the excitation light source provided in the optical repeater located at the final stage of the optical communication path is reduced, the communication quality is deteriorated. Can be suppressed.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described.

The block configuration and the redundant configuration of the optical relay system according to the present embodiment are the same as those in the optical relay system according to the third embodiment. In the optical relay system according to the present embodiment, the configuration of the optical relay station included in the optical relay system is different from the configuration of the optical relay station 300 according to the third embodiment.

FIG. 7 shows the configuration of the optical relay station 400 as the optical relay station n.

The optical relay station 400 has a configuration in which the output light directed to the first optical communication path 2101 (UP side path) of the output light of the 3 dB coupler 240 is branched by the coupler 441. Then, one of the branched output lights is configured to be incident on the EDFA 212 of the second optical communication path 2102 (DOWN side path) from the rear via the WDM coupler 452. Other configurations are the same as the configuration of the optical relay station 300 according to the third embodiment.

The configuration of the optical relay station 1 is the first optical communication path 2101 (UP side path) and the second optical communication path 2102 (DOWN side path) in the configuration of the optical relay station 400 as the optical relay station n described above. ) Can be replaced to form a similar configuration.

Next, the operation of the optical relay station 400 will be described. In FIG. 7, the numbers in the vicinity of the laser elements 321-23, 3dB coupler 240, coupler 441, and WDM couplers 252, 452 indicate the relative optical power of the excitation light at the same location.

FIG. 8 shows the excitation light power injected into the EDFA211 and EDFA212 at the optical relay station 400. In the figure, the optical relay station 400 is in a normal operating state, that is, the laser elements 321 to 323 (LD1 to LD3) are all in a non-failed state, and one of the LD1 to LD3 is in a failed state and the optical output is output. The relative values of the excitation light power when is zero are shown.

In the optical relay station 300 according to the third embodiment, the excitation light powers incident on the EDFA211 and the EDFA212 in the normal operating state (non-failure state) are different (see the top line of FIG. 6).

On the other hand, in the optical relay station 400 according to the present embodiment, the excitation light power incident on the EDFA211 and the EDFA212 can be made equal by the above-described configuration shown in FIG. 7 (top line of FIG. 8). See). That is, the optical relay station 400 as the optical relay station n (second relay station) has the magnitude of the optical power for exciting the EDFA211 (first optical amplifier) during the operation of the excitation lasers (LD1 to LD3). The magnitudes of the optical powers that excite the EDFA212 (second optical amplifier) are configured to be equal.

Similarly, the optical relay station 1 (first relay station) has the magnitude of the optical power for exciting the EDFA211 (first optical amplifier) and the EDFA212 (first relay station) during the operation of the excitation lasers (LD1 to LD3). It can be configured so that the magnitudes of the optical powers that excite (2 optical amplifiers) are equal.

With such a configuration, according to the optical relay station 400 of the present embodiment, it is not necessary to significantly change the specifications of the EDFA211 and the EDFA212, so that the effect of facilitating the design can be obtained.

Further, in the optical relay system according to the present embodiment, the number of redundant excitation lasers is increased only in the DOWN side path of the optical relay station 1 where the self-healing effect cannot be obtained and the UP side path of the optical relay station n. It is supposed to be. Therefore, the number of excitation lasers can be minimized. That is, according to the optical relay system of the present embodiment, the device configuration of the optical relay station can be simplified and the cost can be reduced. Further, as in the case of the optical relay system 2000 according to the second embodiment described above, even if the output of the excitation light source provided in the optical repeater located at the final stage of the optical communication path is reduced, the communication quality is deteriorated. Can be suppressed.

It is said that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Not to mention.

100 Optical relay system 110 Optical communication path 120 Optical repeater 121 First optical repeater 122 Second optical repeater 123 Third optical repeater 200, 300 Optical relay station 211, 212 EDFA
221 222, 223, 224, 321, 322, 323 Laser elements 231 and 232 Polarization synthesis coupler 240 3dB coupler 251, 252, 351 and 452 WDM coupler 261, 262, 263, 264 isolator 271, 272 Optical filter 441 Coupler 1001 Transmitting station 1002 Receiving station 2000 Optical relay system 2001 First base station 2002 Second base station 2100 Optical communication path 2101 First optical communication path 2102 Second optical communication path 2200 Optical relay station 5000 Related optical submarine relay system 5001, 5002 Land station 5100 Optical fiber 5101, 5102 Optical fiber path 5200 Optical repeater 500 Optical repeater 511, 512 Elbium-doped fiber 520 Pump laser 530 Drive circuit

Claims (7)

Of the plurality of optical repeaters located at a plurality of locations in the optical communication path, the optical repeater located at the final stage of the optical communication path.
An optical amplification means that amplifies an optical signal,
And excitation means for outputting pumping light to said optical amplifying means,
With
The redundancy of the excitation laser provided by the excitation means is higher than the redundancy of the excitation laser provided by the excitation means in the optical repeater located at a position other than the final stage among the plurality of optical repeaters. , Optical repeater. The optical repeater according to claim 1, wherein the number of excitation lasers included in the excitation means is larger than the number of excitation lasers included in the excitation means located in a position other than the final stage. The optical repeater according to claim 1, wherein the magnitude of the excitation light output by the excitation means is larger than the magnitude of the excitation light output by the excitation means in the optical repeater located at a position other than the final stage. The optical repeater according to any one of claims 1, 2, and 3, wherein the optical repeater located at a position other than the final stage is located at a point between the transmitting station and the receiving station. The optical repeater according to claim 4 , wherein the point where the optical repeater located other than the final stage is located further includes a point adjacent to the transmitting station. A transmitting station that outputs an optical signal to the first optical fiber,
A first optical repeater that amplifies the optical signal from the first optical fiber.
The first optical repeater is
An optical amplification means for amplifying the optical signal and
And excitation means for outputting pumping light to said optical amplifying means,
Have,
The first optical repeater outputs the amplified optical signal to the second optical repeater via the second optical fiber.
An optical communication system characterized in that the redundancy of the excitation laser included in the excitation means is higher than the redundancy of the excitation laser included in the excitation means included in the second optical repeater. In the final stage of an optical communication path configured to guide an optical signal from a transmitting station to a receiving station
Receiving the optical signal transmitted through the first optical fiber from the transmitting station,
A method for optically amplifying the optical signal it receives,
A step of outputting excitation light used for optical amplification of the optical signal, and
And outputting to the receiving station the optical signal optically amplified through the second optical fiber,
Including
An optical communication method, characterized in that the redundancy of the excitation laser that generates the excitation light is higher than the redundancy of the excitation laser that generates the excitation light in an optical repeater located at a position other than the final stage.

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