Fiber sensing using supervisory path of submarine cables

Patent metadata

Field	Value
Publication number	US-12332394-B2
Application number	US-202217829284-A
Country	US
Kind code	B2
Filing date	May 31, 2022
Priority date	Jun 1, 2021
Publication date	Jun 17, 2025
Grant date	Jun 17, 2025

Abstract

Earthquake detection via fiber sensing is provided using using a supervisory path of submarine cables wherein the supervisory system/path of a submarine optical cable conveys portion(s) of an optical signal back to an origin location periodically—i.e., at every repeater location. Advantageously, since it is known where a returning signal is coming from, a resolution equivalent to an undersea span length may be determined—which is sufficient for wide area disturbances such as earthquakes. The returned signal is sufficiently strong such that the signal-to-noise ratio of a returned/received signal is not limited by the ASE noise of the amplifiers. The returned signal is much larger as compared to a normal distributed acoustic sensing (DAS) return signal since the return signal according to aspects of the present disclosure is directed backward via an optical coupler/reflector/circulator having a much larger coupling ratio as compared to normal Rayleigh back scattering utilized in DAS.

First claim

The invention claimed is:

1. An earthquake sensing method comprising:
providing a submarine/undersea fiber optic communications system, the fiber optic communications system comprising a forward fiber and a backward fiber, the forward fiber and the backward fiber each including a plurality of spans of optical fiber, each span of the plurality of spans having a repeater, each repeater configured to receive optical signals, separate a portion of the received optical signals, and redirect the separated portion to the backward fiber;
providing a sensor transmitter and a sensor receiver, the sensor transmitter in optical communication with the forward fiber, and the sensor receiver in optical communication with the backward fiber, the sensor transmitter configured to generate optical signals and apply the generated optical signals to the forward fiber, the sensor receiver configured to receive, from the backward fiber, portions of the generated optical signals separated by the repeaters; and
determining, from the received portions of the optical signals, seismic activity including earthquakes affecting the submarine/undersea fiber optic communication system;
wherein the sensor transmitter and sensor receiver operate using a double-pulse, double-differentiation technique.

Assignees

• Nec Lab America Inc
• Nec Corp

Inventors

• Yaman Fatih
• Huang Yue-Kai
• Ip Ezra
• Batshon Hussam
• Rodriguez Eduardo Mateo
• Nakamura Kohei
• Inoue Takanori
• Inada Yoshihisa

Classifications

• H04B10/25

  Arrangements specific to fibre transmission · CPC title

• G01V1/226

  Optoseismic systems · CPC title

• G01V1/01 Primary

  Measuring or predicting earthquakes · CPC title