Granted Patent B2

US 12,287,235 · App. 18/370,963 · Granted Apr 29, 2025

Inventors: Mahmoud Farhadiroushan (Elstree, GB); Tom Richard Parker (Elstree, GB); Sergey Shatalin (Elstree, GB)

Assignee: Silixa LTD.

G01H9/004E21B47/002E21B47/107G01D5/35303G01D5/35306G01D5/35325G01D5/35335G01D5/35358G01D5/35364G01D5/35377G01D5/35383G01F1/66G01F1/661G01M11/331G01V1/40E21B47/0025

Abstract

Claims (29)

1. An optical sensing system comprising:

a pulsed light source arranged in use to generate a pulsed optical signal;

an interferometer arranged in use to receive the pulsed optical signal, the interferometer comprising at least two optical paths and at least one frequency shifter arranged in use to introduce a frequency shift between the optical paths in dependence on an RF signal generated by an RF source so as to generate respective pulses having a frequency shift there between;

a sensing fiber arranged in use to receive the respective pulses;

a photodetector arranged in use to receive light backscattered and/or reflected from along the sensing fiber as the respective pulses travel there along and to convert the received light into at least one electrical signal;

means for splitting the at least one electrical signal into a plurality of electrical signals;

a plurality of mixers arranged to receive respectively the plurality of electrical signals, the mixers respectively mixing the plurality of electrical signals with the RF signal at respective different phase angles to down-convert the plurality of electrical signals into a plurality of respective baseband signals; and

a processor arranged to digitize the plurality of respective baseband signals and to determine the relative optical phase modulation at at least one section of the sensing fiber therefrom.

2. A system according to claim 1 , further comprising:

a delay arranged in use to match the path lengths of the interferometer, and a coupler; the delay and the coupler being arranged in use so as to superimpose the respective pulses to generate an interference signal, wherein the coupler is further arranged to introduce relative phase shifts to the interference signal; and

means for monitoring the interference signal at the relative phase shifts.

3. A system according to claim 1 , wherein the sensing fiber is a single mode fiber, polarization maintaining fiber, a single polarization fiber, multimode fiber or a ribbon fiber.

4. A system of according to claim 1 , wherein the system is a distributed acoustic sensor system.

5. A method of fiber optic sensing, comprising:

generating a pulsed optical signal using a pulsed light source;

receiving the pulsed optical signal at an interferometer having at least two optical paths;

introducing a relative frequency shift between the at least two optical paths using at least one frequency shifter in dependence on an RF signal to generate respective pulses having a frequency shift there between;

inputting the respective pulses into a sensing fiber;

receiving light backscattered and/or reflected from along the sensing fiber as the respective pulses travel there along;

converting the received light into at least one electrical signal;

splitting the at least one electrical signal into a plurality of electrical signals;

mixing the plurality of electrical signals with the RF signal at respective different phase angles to down-convert the plurality of electrical signals into a plurality of respective baseband signals;

digitizing the plurality of respective baseband signals; and

determining the relative optical phase modulation at at least one section of the sensing fiber therefrom.

6. A method according to claim 5 , further comprising:

superimposing the respective pulses to generate an interference signal;

introducing a relative phase shift to the interference signal; and

monitoring the interference signal at relative phase shifts.

7. A method according to claim 5 , wherein the method is a method of distributed acoustic sensing.

Assignments (1)

Priority Claims (2)

Continuity (5)

References Cited (332)