Quasi-distributed sensing using enhanced sensing structures

1 . A system for distributed acoustic sensing comprising:

a distributed acoustic sensing (DAS) station to launch a DAS signal into a DAS fiber; and

an enhanced sensing array, the enhanced sensing array comprising at least one sensing component embodied in a cable joint, the at least one sensing component comprising:

a DAS fiber coil, forming a portion of the DAS fiber; and

a low elastic modulus outer shell, surrounding the DAS fiber coil.

2 . The system of claim 1 , the low elastic modulus outer shell comprising polyethylene.

3 . The system of claim 1 , wherein the at least one sensing component comprises at least three enclosures, wherein a first separation between a first sensing component, located nearest to the DAS station, and a second sensing component, located second-nearest to the DAS station, is greater than a second separation between the second sensing component and a third sensing component, located third nearest the DAS station.

4 . The system of claim 1 , wherein the at least one sensing component comprises a plurality of enclosures, arranged in a plurality of cable joints, respectively, each cable joint including a local DAS fiber coil, wherein at least one cable joint is arranged within one or more spans of a multi-span communications system.

5 . The system of claim 4 , wherein the DAS fiber forms a first fiber of a fiber pair, wherein the first fiber is coupled to a DAS transmitter at the DAS station to conduct an outbound signal, and

wherein a second fiber of the fiber pair is arranged to conduct a return signal to a receiver at the DAS station, the return signal being derived from the outbound signal after routing through a loopback located at the one or more spans.

6 . The system of claim 4 , wherein a plurality of cable joints is arranged within a given span of the multi-span communications system.

7 . The system of claim 6 , where a first cable joint of the plurality of cable joints, located relatively closer to the DAS station, includes an unenhanced fiber coil segment, and wherein a second cable joint of the plurality of cable joints, located relatively further from the DAS station, includes an enhanced fiber coil segment, wherein the enhanced fiber coil segment has a relatively higher Rayleigh backscattering coefficient than the unenhanced fiber coil segment.

8 . The system of claim 1 , wherein the enhanced sensing array comprises at least two sensing components, arranged as at least two cable joints, respectively, wherein a first cable joint of the at least two cable joints, located relatively closer to the DAS station, includes an unenhanced fiber coil segment, and wherein a second cable joint of the at least two cable joints, located relatively further from the DAS station, includes an enhanced fiber coil segment, wherein the enhanced fiber coil segment has a relatively higher Rayleigh backscattering coefficient than the unenhanced fiber coil segment.

9 . A system for distributed acoustic sensing, comprising:

a distributed acoustic sensing (DAS) station to launch a DAS signal into a DAS fiber within an optical cable;

an enhanced sensing array, the enhanced sensing array comprising a plurality of sensing components formed in select ones of a plurality of cable joints along the optical cable, arranged over a plurality of spans, wherein a given sensing component of the plurality of sensing components comprises:

a DAS fiber coil, forming a portion of the DAS fiber; and

a low elastic modulus outer shell, surrounding the DAS fiber coil.

10 . The system of claim 9 , each cable joint of the plurality of cable joints including a local DAS fiber coil, wherein a given cable joint is arranged within a given span of a multi-span communications system.

11 . The system of claim 9 , the low elastic modulus outer shell comprising polyethylene.

12 . The system of claim 9 , wherein the DAS fiber forms a first fiber of a fiber pair, wherein the first fiber is coupled to a DAS transmitter at the DAS station to conduct an outbound signal, and

wherein a second fiber of the fiber pair is arranged to conduct a return signal to a receiver at the DAS station, the return signal being derived from the outbound signal after routing through a loopback located at the one or more spans.

13 . The system of claim 10 , wherein each span of the multi-span communications system includes just one cable joint, having a DAS fiber coil.

14 . The system of claim 10 , where a given span of the multi-span communications system comprises:

a first cable joint, located relatively closer to the DAS station, the first cable joint including an unenhanced fiber coil segment; and

a second cable joint, located relatively further from the DAS station, the second cable joint including an enhanced fiber coil segment, wherein the enhanced fiber coil segment has a relatively higher Rayleigh backscattering coefficient than the unenhanced fiber coil segment.

15 . A method for distributed acoustic sensing comprising:

launching an outbound distributed acoustic sensing (DAS) signal from a DAS station into a DAS fiber;

conducting the outbound DAS signal through a sensing array that includes a plurality of sensing components arranged in a plurality of cable joints, each sensing component formed of a low elastic modulus material and including a local DAS fiber coil that forms a portion of the DAS fiber wherein the sensing component is one of a plurality of sensing components, arranged in a plurality of cable joints, respectively in a plurality of spans of a multi-span communications system; and

measuring a power, phase, frequency, or polarization of a reflected signal based upon the outbound DAS signal after the outbound DAS signal traverses the DAS fiber coil.

16 . The method of claim 15 , wherein the plurality of sensing components are arranged in linear fashion.

17 . The method of claim 15 , wherein the DAS fiber forms a first fiber of a fiber pair, wherein the first fiber is coupled to a DAS transmitter at the DAS station to conduct an outbound signal, and

wherein a second fiber of the fiber pair is arranged to conduct a return signal to a receiver at the DAS station, the return signal being derived from the outbound signal after routing through a loopback located at the plurality of spans.