Detecting broadside acoustic signals with a fiber optical distributed acoustic sensing (das) assembly

A distributed fiber optic acoustic sensing system comprising:

• a cable having a cable length, the cable comprising:
• an elongated body having an outer surface;
• at least one straight optical fiber extending parallel to a longitudinal axis of the cable along the cable length;
• and
• at least one helically wrapped optical fiber extending along the cable length and having a first predetermined wrap angle;
• and
• light transmitting and receiving means optically connected to said optical fibers for, respectively, transmitting optical signals into each of the optical fibers and receiving a backscattered component of said signals out of the optical fibers.

A distributed fiber optic acoustic sensing system comprising:

• a cable having a cable length, the cable comprising:
• an elongated body having an outer surface;
• at least one straight optical fiber extending parallel to a longitudinal axis of the cable along the cable length;
• and
• at least two orthogonal sinusoidal optical fibers extending along the cable length;
• and
• light transmitting and receiving means optically connected to said optical fibers for, respectively, transmitting optical signals into each of the optical fibers and receiving a backscattered component of said signals out of the optical fibers.