# US 12,111,204 B2 · Extending dynamic acoustic sensing range and localization in undersea cables using loopbacks

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 12,111,204 B2
- Document ID: US12111204B2
- Status: Granted
- Kind: B2
- Application number: 17/749,420
- Filed: 2022-05-20
- Published: 2022-12-15
- Granted: 2024-10-08
- Earliest claimed: 2021-06-15
- Assignees: Subcom, LLC
- Applicants: Subcom, LLC
- Inventors: Alexei N. Pilipetskii; Maxim A. Bolshtyansky; Dmitri G. Foursa; Georg Heinrich Mohs; Jin-Xing Cai
- Web page: https://patentgrep.com/patent/US12111204B2

## CPC

- G01H 9/004: {using fibre optic sensors (light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125)}
- H04B 10/071: using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
- G01D 5/35361: {using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering}
- G01H: MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- H04B: TRANSMISSION
- G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR

## Abstract

Apparatus, systems, and techniques for extending distributed acoustic sensing (DAS) range in undersea optical cables over multiple spans, as well as providing span-specific DAS information, are provided.

## Claims

### Claim 1

A system comprising:
a DAS interrogator to launch an outbound DAS signal;
an outbound signal path for transmitting the outbound DAS signal over at least one outbound optical fiber;
a plurality of outbound amplifiers, coupled along the outbound signal path, and separated from one another by a distance defining a span;
a return signal path for conducting a plurality of return DAS signals based upon the outbound DAS signal, over a return optical fiber;
a plurality of return amplifiers, coupled along the return signal path, and separated from one another by a distance defining a span;
a plurality of loopbacks, to reroute the outbound DAS signal between the outbound signal path and the return signal path, to form the plurality of return DAS signals; and
a loopback component, arranged in at least one loopback of the plurality of loopbacks, to regulate transmission of a return DAS signal from the loopback to the DAS interrogator.

### Claim 2 (depends on 1)

The system of claim 1, the loopback component comprising an optical filter.

### Claim 3 (depends on 2)

The system of claim 2, further comprising a loopback amplifier, disposed in the loopback.

### Claim 4 (depends on 1)

The system of claim 1, the loopback component comprising an optical switch.

### Claim 5 (depends on 4)

The system of claim 4, wherein the optical switch is switchable by mechanical means, electrical means, electromechanical means, or electrooptical means.

### Claim 6 (depends on 5)

The system of claim 5, further comprising a loopback amplifier, and a bandpass filter, disposed in the loopback.

### Claim 7 (depends on 6)

The system of claim 6, wherein the bandpass filter is placed between the loopback amplifier and the return signal path.

### Claim 8 (depends on 1)

The system of claim 1, wherein at least some amplifiers of the outbound amplifiers, return amplifiers, or a combination thereof are erbium doped fiber amplifiers, other rare earth doped fiber amplifiers, Raman amplifiers, semiconductor optical amplifiers, or combination thereof.

### Claim 9

A method, comprising:
launching a DAS signal from a DAS interrogator over an outbound DAS signal path, comprising at least one optical fiber;
amplifying the outbound DAS signal at a plurality of amplifiers along the outbound DAS signal path, the plurality of amplifiers being distributed over a plurality of spans;
routing the outbound DAS signal into a plurality of loopbacks arranged between the outbound DAS signal path and a return DAS signal path;
transmitting, along the return signal path, at least one return DAS signal from at least one loopback of the plurality of loopbacks to the DAS interrogator; and
amplifying the at least one return DAS signal,
wherein the at least one return DAS signal is processed by a component located at the at least one loopback to provide span-specific DAS information to the DAS interrogator.

### Claim 10 (depends on 9)

The method of claim 9, wherein an optical filter is disposed in at least one loopback of the plurality of loopbacks.

### Claim 11 (depends on 10)

The method of claim 10, wherein a loopback amplifier, disposed in the at least one loopback.

### Claim 12 (depends on 9)

The method of claim 9, wherein an optical switch is disposed in at least one loopback of the plurality of loopbacks.

### Claim 13 (depends on 12)

The method of claim 12, wherein the optical switch is switchable by mechanical means, electrical means, electromechanical means, or electrooptical means.

### Claim 14 (depends on 13)

The method of claim 13, further comprising a loopback amplifier, and a bandpass filter, disposed in the at least one loopback.

### Claim 15 (depends on 14)

The method of claim 14, wherein the bandpass filter is placed between the loopback amplifier and the return signal path.

### Claim 16 (depends on 9)

The method of claim 9, wherein at least some amplifiers of the outbound amplifiers, return amplifiers, or a combination thereof are erbium doped fiber amplifiers, other rare earth doped fiber amplifiers, Raman amplifiers, semiconductor optical amplifiers, or combination thereof.

### Claim 17

A system comprising:
a DAS interrogator to launch an outbound DAS signal;
an outbound signal path for transmitting the outbound DAS signal over at least one outbound optical fiber;
a plurality of outbound amplifiers, coupled along the outbound signal path, and separated from one another by a distance defining a span;
a return signal path for conducting a plurality of return DAS signals based upon the outbound DAS signal, over a return optical fiber;
a plurality of return amplifiers, coupled along the return signal path, and separated from one another by a distance defining a span;
a plurality of loopbacks, to reroute the outbound DAS signal between the outbound signal path and the return signal path, to form the plurality of return DAS signals;
a loopback component, arranged in at least one loopback of the plurality of loopbacks, to regulate transmission of a return DAS signal from the loopback to the DAS interrogator; and
an optical amplifier, disposed in the at least one loopback.

### Claim 18 (depends on 17)

The system of claim 17, the loopback component comprising an optical filter.

### Claim 19 (depends on 17)

The system of claim 17, the loopback component comprising an optical switch.

### Claim 20 (depends on 19)

The system of claim 19, wherein the optical switch is switchable by mechanical means, electrical means, electromechanical means, or electrooptical means.