Method and system for an ultimately fast frequency-scanning brillouin optical time domain analyzer
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.
1. A method 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 in a plurality of locations along the optical fiber;
deriving, a local Brillouin Frequency Shift (BFS), in said plurality of locations along the optical fiber, wherein said local BFS is the pump-probe frequency difference which maximizes the Brillouin gain on the BGS;
determining strain and/or temperature in said plurality of locations along the optical fiber, based on the respective local BFS; and
evaluating dynamic structural changes to a structure to which the optical fiber is attached thereto, or planted therein, based on the determined strain or temperature.
2. 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 allowing a dynamic sensing of strain and temperature.
3. A system 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:
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 in a plurality of locations along the optical fiber;
derive, the local Brillouin Frequency Shift (BFS), in said plurality of locations 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 said plurality of locations along the optical fiber, based on the respective local BFS,
wherein the system is further configured to evaluate dynamic structural changes to a structure to which the optical fiber is attached thereto, or planted therein, based on the determined strain or temperature.
4. The system according to claim 3 , wherein the scanning, the deriving, and the determining are repeated sufficiently fast so that the optical fiber is sampled throughout its length allowing a dynamic sensing of strain and temperature.