Optical transmission system, and optical transmission method
The optical transmission system of the present invention includes a multi-core transmission path which includes a plurality of cores, and in which optical signals propagate through the plurality of cores, a first optical repeating means for amplifying the optical signals by individually exciting first multi-core optical amplification mediums, and a second optical repeating means for amplifying the optical signals by collectively exciting second multi-core optical amplification mediums, wherein the first optical repeating means is positioned spaced apart from the second optical repeating means by a distance determined on the basis of either a first transmissible distance due to the first optical repeating means and a second transmissible distance due to the second optical repeating means.
1 . An optical transmission system comprising:
a multi-core optical transmission path that includes a plurality of cores, and in which an optical signal propagates through the plurality of cores;
a first optical amplifier configured to amplify the optical signal by individually exciting a first multi-core optical amplification medium; and
a second optical amplifier configured to amplify the optical signal by collectively exciting a second multi-core optical amplification medium, wherein
a first transmittable distance by the first optical amplifier is equal to a second transmittable distance by the second optical amplifier, and
the first optical amplifier and the second optical amplifier are positioned alternately.
2 . The optical transmission system according to claim 1 , wherein
the first optical amplifier and the second optical amplifier constitute an optical amplifier group including at least one of the first optical amplifier and at least one of the second optical amplifier, and
the first optical amplifier included in each optical amplifier group is configured to amplify the optical signal in such a way that a difference in optical intensity of the optical signal between the plurality of cores is reduced.
3 . The optical transmission system according to claim 2 , wherein
the optical amplifier group includes a previous-stage optical amplifier group and a subsequent-stage optical amplifier group,
the previous-stage optical amplifier group is positioned on a previous-stage side of the subsequent-stage optical amplifier group, and
a previous-stage first optical amplifier being the first optical amplifier belonging to the previous-stage optical amplifier group is configured to amplify the optical signal in such a way that a difference in optical intensity of the optical signal among the plurality of cores in a subsequent-stage first optical amplifier being the first optical amplifier belonging to the subsequent-stage optical amplifier group is reduced.
4 . The optical transmission system according to claim 3 , further comprising
a controller configured to control the previous-stage first optical amplifier and the subsequent-stage first optical amplifier, wherein
the controller is configured to increase optical intensity being output by the previous-stage first optical amplifier, when determining that a difference in optical intensity among the plurality of cores of the optical signal being output by the subsequent-stage first optical amplifier is larger than a predetermined value.
5 . The optical transmission system according to claim 3 , further comprising
a controller configured to control the previous-stage first optical amplifier and the subsequent-stage first optical amplifier, wherein
the controller is configured to increase optical intensity being output by the previous-stage first optical amplifier, when determining that a difference in optical intensity among the plurality of cores of the optical signal being input to the subsequent-stage first optical amplifier is larger than a predetermined value, and a difference in optical intensity among the plurality of cores of the optical signal being output by the previous-stage first optical amplifier is smaller than a predetermined value.
6 . The optical transmission system according to claim 1 , wherein
the first optical amplifier includes a first multi-core optical fiber including the first multi-core optical amplification medium in each core, a plurality of core excitation lasers each of which is configured to generate individual excitation light to excite the first multi-core optical amplification medium individually, and a fan-in/fan-out configured to introduce the individual excitation light into each core of the first multi-core optical fiber, and
the second optical amplifier includes a second multi-core optical fiber including the second multi-core optical amplification medium in each core, and a clad excitation laser configured to generate collective excitation light to excite the second multi-core optical amplification medium collectively.
7 . An optical transmission method comprising:
locating a first multi-core optical amplification medium and a second multi-core optical amplification medium at different positions of a multi-core optical transmission path;
propagating an optical signal through a plurality of cores of the multi-core optical transmission path;
amplifying the optical signal by individually exciting the first multi-core optical amplification medium; and
amplifying the optical signal by collectively exciting the second multi-core optical amplification medium, wherein
the locating the first multi-core optical amplification medium and the second multi-core optical amplification medium includes alternately locating the first multi-core optical amplification medium and the second multi-core optical amplification medium when a first transmittable distance of the optical signal when the first multi-core optical amplification medium is individually excited is equal to a second transmittable distance of the optical signal when the second multi-core optical amplification medium is collectively excited.
8 . The optical transmission method according to claim 7 , further comprising
locating the first multi-core optical amplification medium and the second multi-core optical amplification medium in such a way as to constitute an optical amplification medium group including at least one of the first multi-core optical amplification medium and at least one of the second multi-core optical amplification medium, wherein
the individually exciting the first multi-core optical amplification medium includes amplifying the optical signal in such a way that a difference in optical intensity of the optical signal among the plurality of cores is reduced.
9 . The optical transmission method according to claim 8 , wherein
the optical amplification medium group includes a previous-stage optical amplification medium group and a subsequent-stage optical amplification medium group,
the previous-stage optical amplification medium group is located on a previous-stage side of the subsequent-stage optical amplification medium group, and
the individually exciting a previous-stage first optical amplification medium being the first multi-core optical amplification medium belonging to the previous-stage optical amplification medium group includes amplifying the optical signal in such a way that a difference in optical intensity of the optical signal among the plurality of cores in a subsequent-stage first optical amplification medium being the first multi-core optical amplification medium belonging to the subsequent-stage optical amplification medium group is reduced.
10 . The optical transmission method according to claim 9 , wherein
the individually exciting the previous-stage first optical amplification medium includes amplifying the optical signal when a difference in optical intensity, among the plurality of cores, of the optical signal amplified and output by the subsequent-stage first optical amplification medium is larger than a predetermined value.
11 . The optical transmission method according to claim 9 , wherein
the individually exciting the previous-stage first optical amplification medium includes amplifying the optical signal when a difference in optical intensity, among the plurality of cores, of the optical signal being input to the subsequent-stage first optical amplification medium is larger than a predetermined value, and a difference in optical intensity, among the plurality of cores, of the optical signal amplified and output by the previous-stage first optical amplification medium is smaller than a predetermined value.