US 11,791,922 B2
Transmission device, time transmission system, and delay compensation method
Masahiro Nakagawa, Tokyo (JP); Kaoru Arai, Tokyo (JP); Hiroki Sakuma, Tokyo (JP); and Shunichi Tsuboi, Tokyo (JP)
Assigned to Nippon Telegraph and Telephone Corporation, Tokyo (JP)
Appl. No. 17/429,172
Filed by Nippon Telegraph and Telephone Corporation, Tokyo (JP)
PCT Filed Feb. 6, 2020, PCT No. PCT/JP2020/004618
§ 371(c)(1), (2) Date Aug. 6, 2021,
PCT Pub. No. WO2020/166485, PCT Pub. Date Aug. 20, 2020.
Claims priority of application No. 2019-024802 (JP), filed on Feb. 14, 2019.
Prior Publication US 2022/0103281 A1, Mar. 31, 2022
Int. Cl. H04J 3/06 (2006.01)
CPC H04J 3/0682 (2013.01) [H04J 3/0667 (2013.01); H04J 3/0673 (2013.01)] 3 Claims
OG exemplary drawing
 
3. A delay correction method implemented by a time transmission system, wherein the time transmission system comprises (i) a first transmission device connected to a first time synchronization device and (ii) a second transmission device connected to a time synchronization device, each of the first transmission device comprising:
a transmission section configured to transmit packets for delay calculation for a plurality of wavelengths to the second transmission device simultaneously; and
a reception section configured to:
calculate a first propagation delay on a path from the second transmission device to the first transmission device based on a difference between arrival times of the packets for delay calculation for the plurality of wavelengths received from the second transmission device,
receive a second propagation delay on a path from the first transmission device to the second transmission device calculated by the second transmission device, and
calculate a maximum delay that is larger than any of the first propagation delay and the second propagation delay, wherein
the reception section is further configured to:
calculate a third propagation delay on the path from the second transmission device to the first transmission device based on a difference between arrival times of the packets for time synchronization for the plurality of wavelengths when the packets for time synchronization are received from the second transmission device, and
transmit the received packets for time synchronization to the first time synchronization device after waiting for a time interval that is calculated by subtracting the third propagation delay from the set delay.