Optical communication system and master station

Patent metadata

Field	Value
Publication number	US-2023142562-A1
Application number	US-202017917597-A
Country	US
Kind code	A1
Filing date	Apr 14, 2020
Priority date	Apr 14, 2020
Publication date	May 11, 2023
Grant date	—

Abstract

The present invention enables shortening the time required for resuming communication in a protection method that uses a backup path in an optical communication system that includes a master station device and multiple slave station devices. The slave station devices are connected to a loop path in parallel. The communication paths between the master station device and the slave station devices include a normal path and a backup path. First and second slave station devices are slave station devices that cannot perform communication via the normal path. The magnitude relationship between backup path RTTs is opposite to the magnitude relationship between normal path RTTs. If the second normal path RTT for the second slave station device is longer than the first normal path RTT for the first slave station device, the first backup path RTT is longer than the second backup path RTT, and the second backup path RTT is shorter than the first backup path RTT. Based on this fact, the master station device limits the QuietWindow, which is used in ranging processing for measuring the backup path RTT, to a size smaller than a predetermined maximum size.

First claim

1 . An optical communication system comprising:
a plurality of slave station devices that are connected to a loop path in parallel; and a master station device that is connected to the loop path and configured to perform communication with each of the slave station devices, wherein communication paths between the master station device and each of the slave station devices include:
a normal path that extends along the loop path from the master station device to each of the slave station devices in a first direction, and
a backup path that extends along the loop path from the master station device to each of the slave station devices in a second direction that is opposite to the first direction,
the master station device is configured to execute:
ranging processing for setting a QuietWindow and measuring an RTT (Round Trip Time) between the master station device and each of the slave station devices, and
communication control processing for controlling communication with the slave station devices based on the RTTs,
a normal path RTT is the RTT in a case of communication performed via the normal path, a backup path RTT is the RTT in a case of communication performed via the backup path, a disconnected slave station device is a slave station device that cannot perform communication via the normal path, among the plurality of slave station devices, if the disconnected slave station device does not exist, the master station device executes the communication control processing with respect to the slave station devices based on the normal path RTTs, if the disconnected slave station device is detected, the master station device executes the ranging processing and measures the backup path RTT for the disconnected slave station device, and resumes the communication control processing with respect to the disconnected slave station device based on the backup path RTT, a first slave station device is a disconnected slave station device having a first normal path RTT as the normal path RTT, a second slave station device is a disconnected slave station device having a second normal path RTT as the normal path RTT, the second normal path RTT being longer than the first normal path RTT, a first backup path RTT is the backup path RTT between the master station device and the first slave station device, a second backup path RTT is the backup path RTT between the master station device and the second slave station device, and in the ranging processing for measuring the backup path RTT, based on a fact that the first backup path RTT is longer than the second backup path RTT, and that the second backup path RTT is shorter than the first backup path RTT, the master station device limits the QuietWindow to a size smaller than a predetermined maximum size.

2 . The optical communication system according to claim 1 ,
wherein in the ranging processing for measuring the backup path RTT, the master station device sets the size of the QuietWindow based on an envisioned maximum value and an assumed minimum value of the backup path RTT, the master station device sets the envisioned maximum value of the first backup path RTT to a value less than or equal to a predetermined maximum value, and based on a fact that the second backup path RTT is shorter than the first backup path RTT, the master station device sets the envisioned maximum value of the second backup path RTT to a value that is smaller than the envisioned maximum value of the first backup path RTT.

3 . The optical communication system according to claim 2 ,
wherein after measuring the first backup path RTT, the master station device sets the envisioned maximum value of the second backup path RTT to a value that is less than or equal to the measured first backup path RTT.

4 . The optical communication system according to claim 2 ,
wherein a third slave station device is a slave station device having a third normal path RTT as the normal path RTT, the third normal path RTT being smallest among the plurality of slave station devices, and the master station device sets the envisioned maximum value of the second backup path RTT smaller than the predetermined maximum value by an amount corresponding to a difference between the second normal path RTT and the third normal path RTT.

5 . The optical communication system according to claim 1 ,
wherein in the ranging processing for measuring the backup path RTT, the master station device sets the size of the QuietWindow based on an envisioned maximum value and an assumed minimum value of the backup path RTT, and based on a fact that the first backup path RTT is longer than the second backup path RTT, the master station device sets the envisioned minimum value of the first backup path RTT to a value that is larger than the predetermined minimum value.

6 . The optical communication system according to claim 5 ,
wherein a fourth slave station device is a slave station device having a fourth normal path RTT as the normal path RTT, the fourth normal path RTT being largest among the plurality of slave station devices, and the master station device sets the envisioned minimum value of the first backup path RTT larger than the predetermined minimum value by an amount corresponding to a difference between the fourth normal path RTT and the first normal path RTT.

7 . The optical communication system according to claim 1 ,
wherein an RTT difference is a difference between the second normal path RTT and the first normal path RTT, and after measuring the first backup path RTT, the master station device estimates a range of the second backup path RTT based on the measured backup path RTT and the RTT difference, sets the QuietWindow in accordance with the estimated range of the second backup path RTT, and measures the second backup path RTT.

8 . A master station device that performs communication with each of a plurality of slave station devices in an optical communication system,
wherein the slave station devices are connected to a loop path in parallel, communication paths between the master station device and each of the slave station devices include:
a normal path that extends along the loop path from the master station device to each of the slave station devices in a first direction, and
a backup path that extends along the loop path from the master station device to each of the slave station devices in a second direction that is opposite to the first direction,
the master station device is configured to execute:
ranging processing for setting a QuietWindow and measuring an RTT (Round Trip Time) between the master station device and each of the slave station devices, and
communication control processing for controlling communication with the slave station devices based on the RTTs,
a normal path RTT is the RTT in a case of communication performed via the normal path, a backup path RTT is the RTT in a case of communication performed via the backup path, a disconnected slave station device is a slave station device that cannot perform communication via the normal path, among the plurality of slave station devices, if the disconnected slave station device does not exist, the master station device executes the communication control processing with respect to the slave station devices based on the normal path RTTs, if the disconnected slave station device is detected, the master station device executes the ranging processing and measures the backup path RTT for the disconnected slave station device, and resumes the communication control processing with respect to the disconnected slave station device based on the backup path RTT, a first slave station device is a disconnected slave station device having a first normal path RTT as the normal path RT

Assignees

• Nippon Telegraph & Telephone

Inventors

• Ujikawa Hirotaka
• HARADA Rintaro
• Kaneko Shin

Classifications

• H04Q11/00

  Selecting arrangements for multiplex systems (multiplex systems H04J) · CPC title

• H04L43/0864 Primary

  Round trip delays · CPC title

• H04B10/032 Primary

  using working and protection systems {(H04J14/0287 takes precedence)} · CPC title

• H04B10/2755

  Ring-type networks with a headend · CPC title

• H04Q11/0067

  Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring · CPC title