US 11,855,760 B2
Transmission device, time transmission system, and delay compensation method
Masahiro Nakagawa, Musashino (JP); Kaoru Arai, Musashino (JP); Hiroki Sakuma, Musashino (JP); and Shunichi Tsuboi, Musashino (JP)
Assigned to Nippon Telegraph and Telephone Corporation, Tokyo (JP)
Appl. No. 17/428,240
Filed by Nippon Telegraph and Telephone Corporation, Tokyo (JP)
PCT Filed Feb. 6, 2020, PCT No. PCT/JP2020/004617
§ 371(c)(1), (2) Date Aug. 3, 2021,
PCT Pub. No. WO2020/166484, PCT Pub. Date Aug. 20, 2020.
Claims priority of application No. 2019-024801 (JP), filed on Feb. 14, 2019.
Prior Publication US 2022/0294549 A1, Sep. 15, 2022
Int. Cl. H04J 3/06 (2006.01); H04L 7/00 (2006.01)
CPC H04J 3/0667 (2013.01) [H04J 3/0682 (2013.01); H04L 7/0033 (2013.01)] 3 Claims
OG exemplary drawing
 
1. A transmission device for use in a time transmission system, the time transmission system synchronizing time of a second time synchronization device based on time information of transmission and reception of packets for time synchronization between a first time synchronization device and the second time synchronization device via a first transmission device connected to the first time synchronization device and a second transmission device corresponding to the first transmission device and connected to the second time synchronization device, the transmission device being operable as the first transmission device or the second transmission device, comprising one or more processors configured to:
transmit packets for time synchronization for a plurality of wavelengths to the other transmission device simultaneously, wherein the first transmission device is paired with the first time synchronization device, and the second transmission device is paired with the second time synchronization device,
wherein an uplink wiring length and a downlink wiring length between the first time synchronization device and the first transmission device are the same, and an uplink wiring length and a downlink wiring length between the second transmission device and the second time synchronization device are the same;
receive the packets for time synchronization for the plurality of wavelengths from the other transmission device, measure a propagation delay on a path from the other transmission device to the transmission device based on a difference between arrival times of the received packets for time synchronization for the plurality of wavelengths, wherein measuring the propagation delay comprises:
determining, using the difference between arrival times of the received packets, a length of a downlink transmission line and a length of an uplink transmission line between the first and second transmission devices, and
determining the propagation delay for each of the downlink transmission line and the uplink transmission line using the corresponding length, a temperature correction, and a predetermined delay for each length unit due to temperature change; and
provide the propagation delay to the second time synchronization device as a correction parameter used in a process of synchronizing time of the second time synchronization device.