Method to increase the signal to noise ratio of distributed acoustic sensing by spatial averaging

1. An apparatus for performing distributed acoustic sensing (DAS) in an environment with acoustic vibrations present, comprising:

at least an optical fiber positioned in said environment, wherein the optical fiber comprises N spatial channels and N laser pulses are launched into the N spatial channels of the optical fiber and propagate over a fiber length; and

one or more sensors to measure N signals of acoustic vibration amplitude and frequency from each of N spatial channels, wherein the N signals are digitally added for spatial averaging and applied to determine DAS,

wherein N measured signals of the acoustic vibration(s) amplitude and frequency are digitally added producing a new signal of the acoustic vibration(s) amplitude and frequency,

wherein the SNR of the new signal of the acoustic vibration's amplitude and frequency is increased by a factor of N 1/2 .

2. The apparatus of claim 1 , comprising a processor to digitally add the N signals from the N spatial channels for spatial averaging, wherein a signal to noise ratio (SNR) of the signal of the acoustic vibration is increased by a factor of N 1/2 .

3. The apparatus of claim 1 , wherein the optical fiber is acoustically coupled to vibrations.

4. The apparatus of claim 1 , wherein the environment comprises one of: bridges, tunnels, railroads, buildings, oil wells, borders.

5. The apparatus of claim 1 , wherein the spatial channels comprises multiple optical fibers.

6. The apparatus of claim 1 , wherein the spatial channels comprises a single mode or a multi-mode fiber.

7. The apparatus of claim 1 , wherein the spatial channels comprise cores of a multicore optical fiber and wherein each core comprises a single mode or a multi-mode fiber.

8. The apparatus of claim 1 , wherein the spatial channels comprises spatial modes of one or more multimode optical fibers.

9. The apparatus of claim 1 , wherein the spatial channels comprises spatial modes of cores of a multicore optical fiber.

10. The apparatus of claim 1 , wherein the spatial channels comprises spatial modes of cores of multiple multicore optical fiber.

11. The apparatus of claim 1 , wherein each N spatial channel experiences acoustic vibrations.

12. The apparatus of claim 1 , wherein each spatial channel has an identical response to the acoustic vibration(s) and experiences the same phase of the acoustic vibration(s).

13. The apparatus of claim 1 , wherein each of the N laser pulses launched into the N spatial channels propagating over a length of the optical fiber(s) and creates Rayleigh backscattering at one or more spatial points along the length of the optical fiber(s).

14. The apparatus of claim 13 , wherein for each of the N spatial channels, a phase of a Rayleigh backscattering at a spatial point along the length of the optical fiber(s) is proportional to the amplitude of the acoustic vibration at that spatial point.

15. The apparatus of claim 1 , wherein N signals of the acoustic vibration(s) amplitude and frequency are measured from each of the N spatial channels of the optical fiber(s).

16. The apparatus of claim 1 , wherein N signals are measured using a phase of the Rayleigh backscattering and optical time domain reflectometry (OTDR) traces.

17. The apparatus of claim 1 , wherein N signals of the acoustic vibration(s) amplitude and frequency are measured from the Rayleigh backscattering from each of the N spatial channels of the optical fiber(s) using N interrogators.

18. The apparatus of claim 17 , comprising an interferometer to measure a phase of Raleigh backscattering.

19. The apparatus of claim 18 , wherein the interferometer comprises one of: a self-referenced unit, a local oscillator, a heterodyne oscillator, a homodyne oscillator, a Mach-Zender interferometer, a Michelson interferometer.