US 11,996,895 B2
Optical communication system and control method
Kazutaka Hara, Musashino (JP); Yasutaka Kimura, Musashino (JP); and Atsuko Kawakita, Musashino (JP)
Assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
Appl. No. 17/798,068
Filed by NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
PCT Filed Feb. 12, 2020, PCT No. PCT/JP2020/005333
§ 371(c)(1), (2) Date Aug. 5, 2022,
PCT Pub. No. WO2021/161414, PCT Pub. Date Aug. 19, 2021.
Prior Publication US 2023/0082934 A1, Mar. 16, 2023
Int. Cl. H04B 10/61 (2013.01); H04B 10/25 (2013.01)
CPC H04B 10/614 (2013.01) [H04B 10/25891 (2020.05)] 6 Claims
OG exemplary drawing
 
1. An optical communication system comprising a single unequal branch optical splitter which is configured to vary a branching ratio of light and a control apparatus,
the unequal branch optical splitter including:
a single merge port to which an OLT (Optical Line Terminal) is connected;
N-number (where N is an integer equal to or larger than 2) of branch ports to which a PON (Passive Optical Network) including an ONU (Optical Network Unit) is connected; and
N−1-number of branch units including a single first port on a side of the merge port, two second ports on a side of the branch port, and a varying mechanism which varies the branching ratio of light from the first port to each of the second ports under an instruction from the control apparatus, wherein
the branch units are coupled such that one of the second ports is connected to the branch port and the other of the second ports is connected to the first port of the branch unit of a next stage,
in the branch unit of a first stage among the branch units, the first port is connected to the merge port, and in the branch unit of a final stage, the second ports are respectively connected to the branch port, and
the control apparatus is configured to perform one of a first process and a second process,
in the first process:
the control apparatus includes a management information database which stores information of the branch ports to which the ONUs are connected and distances between the OLT and each of the ONUs;
when a new ONU of the ONUs is connected and a distance between the new ONU and the OLT is longer than any of the distances stored in the management information database, the control apparatus is configured to:
instruct the varying mechanism to set the branching ratio of light to the branch port to which the new ONU is connected to 100%;
perform ranging with respect to the new ONU and acquire a distance between the new ONU and the OLT as a result of the ranging;
calculate the branching ratio of light to each of the branch ports based on all of the distances including the distance to the new ONU; and
instruct all of the varying mechanisms so that the branching ratio of light is set, and
in the second process:
when a discovery function of the control apparatus detects that a new ONU of the ONUs is connected, the control apparatus is configured to:
instruct, for each of the branch ports, the varying mechanism to set the branching ratio of light to the branch port to 100%;
perform ranging with respect to all of the ONUs connected to the branch port;
acquire distances between each of the ONUs and the OLT;
calculate the branching ratio of light to each of the branch ports based on all of the distances obtained as a result of the ranging after performing the ranging with respect to all of the branch ports; and
instruct all of the varying mechanisms so that the branching ratio of light is set.