Simultaneous distributed acoustic sensing with multiple gauge lengths

A method for distributed acoustic sensing comprising:

• sending optical pulses at a fixed rate with varying pulse widths down an optical fiber to adjust a spatial resolution of a distributed acoustic sensing system, wherein light from the optical pulses sent at the fixed rate with the varying pulse widths is backscattered from positions along a length of the optical fiber;
• splitting the backscattered light from the optical pulses sent at the fixed rate with the varying pulse widths into a first portion for a first interferometer and a second portion for a second interferometer, the first interferometer having a first gauge length, a first arm, and a second arm, and the second interferometer having a second gauge length, wherein;
• the first arm of the first interferometer has a first path length, the second arm of the first interferometer has a second path length,
• a path length difference corresponds to a difference between the first path length and the second path length of the first interferometer, and
• the first gauge length is different from the second gauge length;
• changing the path length difference of the first interferometer to further adjust the spatial resolution of the distributed acoustic sensing system;
• detecting a first interferometric signal from the first interferometer responsive to the first portion of backscattered light;
• detecting a second interferometric signal from the first interferometer responsive to the second portion of backscattered light;
• and
• processing the first and the second interferometric signals for at least two different sensing applications adapted for the first and the second gauge lengths, respectively, wherein the processing of the first and the second interferometric signals for the at least two different sensing applications is based on the optical pulses being transmitted at the fixed rate with the varying pulse widths.

A non-transitory computer-readable storage medium having embodied thereon instructions that when executed by one or more processors implement a method for distributed acoustic sensing, the method comprising:

• initiating transmission of optical pulses at a fixed rate with varying pulse widths down an optical fiber to adjust a spatial resolution of a distributed acoustic sensing system, wherein light associated with the optical pulses transmitted at the fixed rate with the varying pulse widths is backscattered from positions along a length of the optical fiber;
• splitting the backscattered light into a first portion for a first interferometer and a second portion for a second interferometer, the first interferometer having a first gauge length a first arm, and a second arm, and the second interferometer having a second gauge length, wherein:
• the first arm of the first interferometer has a first path length, the second arm of the first interferometer has a second path length,
• a path length difference corresponds to a difference between the first path length and the second path length of the first interferometer, and
• the first gauge length is different from the second gauge length;
• changing the path length difference of the first interferometer to further adjust the spatial resolution of the distributed acoustic sensing system;
• detecting a first interferometric signal from the first interferometer responsive to the first portion of backscattered light;
• detecting a second interferometric signal from the first interferometer responsive to the first portion of backscattered light;
• and
• processing the first and the second interferometric signals for at least two different sensing applications adapted for the first and the second gauge lengths, respectively, wherein the processing of the first and the second interferometric signals for the at least two different sensing applications is based on the pulses being transmitted at the fixed rate with the varying pulse widths.