Method and system for an ultimately fast frequency-scanning brillouin optical time domain analyzer

Patent metadata

Field	Value
Publication number	US-2016273998-A1
Application number	US-201615077264-A
Country	US
Kind code	A1
Filing date	Mar 22, 2016
Priority date	Mar 22, 2015
Publication date	Sep 22, 2016
Grant date	—

Abstract

A method and a system for ultimately fast frequency-scanning Brillouin optical time domain analysis are provided herein. The method may include: simultaneously launching two pairs each having a pulsed pump wave and a counter-propagating constant wave (CW) probe wave, into an optical fiber, wherein the pulsed pumps have orthogonal States of Polarization (SOPs), and wherein the two CW probe waves have a same SOP; scanning common pump-probe frequency difference, over a frequency range that encompasses a respective Brillouin Gain Spectrum (BGS) and current and expected spectral shifts of the BGS along the optical fiber; deriving, a local Brillouin Frequency Shift (BFS), in a distributed manner along the optical fiber, which is defined as the pump-probe frequency difference which maximizes the Brillouin gain on the BGS; and determining strain and/or temperature in a distributed manner along the optical fiber, based on the respective local BFS.

First claim

1 . A method for ultimately fast frequency-scanning Brillouin optical time domain analysis comprising:
simultaneously launching two pairs of optical signals into an optical fiber, each pair comprising a pulsed pump wave and a counter-propagating constant wave (CW) probe wave, wherein the pulsed pumps have orthogonal States of Polarization (SOPs), and wherein the two CW probe waves have a same SOP; scanning common pump-probe frequency difference, over a frequency range that encompasses a respective Brillouin Gain Spectrum (BGS) and current and expected spectral shifts of the BGS along the optical fiber; deriving, a local Brillouin Frequency Shift (BFS), in a distributed manner along the optical fiber, wherein said local BFS is the pump-probe frequency difference which maximizes the Brillouin gain on the BGS; and determining strain and/or temperature in a distributed manner along the optical fiber, based on the respective local BFS.

2 . The method according to claim 1 , wherein the optical fiber is of the order of 1 km or shorter.

3 . The method according to claim 1 , wherein the fiber is selected so as to minimize polarization mode dispersion (PMD) occurrence in the optical fiber.

4 . The method according to claim 1 , wherein the scanning, the deriving, and the determining are repeated sufficiently fast so that the optical fiber is sampled throughout its length in a dynamic manner.

5 . The method according to claim 1 , wherein the determining is usable to evaluate dynamic structural changes to a structure to which the optical fiber is attached thereto, or planted therein.

6 . A system for ultimately fast frequency-scanning Brillouin optical time domain analysis comprising:
at least one light source; an optical fiber; a controller configured to instruct the light source to simultaneously launch two pairs of optical signals into said optical fiber, each pair having a pulsed pump wave and a counter-propagating constant wave (CW) probe wave, wherein the pulsed pumps have orthogonal States of Polarization (SOPs), and wherein the two CW probe waves have a same SOP; a sensor configured to measure outputs of the optical fiber; and a computer processor configured to receive outputs of the optical sensor and to:
scan common pump-probe frequency difference, over a frequency range that encompasses a respective Brillouin Gain Spectrum (BGS) and current and expected spectral shifts of the BGS along the optical fiber;
derive, the local Brillouin Frequency Shift (BFS), in a distributed manner along the optical fiber, which is defined as the pump-probe frequency difference which maximizes the CW probe Brillouin gain; and
determine strain and/or temperature in a distributed manner along the optical fiber, based on the respective local BFS.

7 . The system according to claim 6 , wherein the optical fiber is of the order of 1 km or shorter.

8 . The system according to claim 6 , wherein the fiber is selected so as to minimize polarization mode dispersion (PMD) occurrence in the optical fiber

9 . The system according to claim 6 , wherein the scanning, the deriving, and the determining are repeated sufficiently fast so that the optical fiber is sampled throughout its length in a dynamic manner.

10 . The system according to claim 6 , wherein the determining is usable to evaluate dynamic structural changes to a structure to which the optical fiber is attached thereto, or planted therein.

Assignees

• Ramot At Tel-Aviv Univ Ltd

Inventors

• Tur Moshe
• Sovran Ido
• Motil Avi

Classifications

• G01M11/3127 Primary

  using multiple or wavelength variable input source · CPC title

• G01M11/39 Primary

  in which light is projected from both sides of the fiber or waveguide end-face · CPC title

• G01M11/319 Primary

  Reflectometers using stimulated back-scatter, e.g. Raman or fibre amplifiers · CPC title

• G01M11/00

  Testing of optical apparatus; Testing structures by optical methods not otherwise provided for · CPC title