Distributed optical sensing using compressive sampling
Distributed optical sensing systems utilize compressive sensing techniques to determine parameters sensed by a waveguide. The system generates light that is sent along a sensing waveguide, thereby producing backscattered light. A compressive sampling filter forms part of the system, and is used to selectively block portions of the generated light or the backscattered light. The backscattered light is received by a receiver and used to determine one or more parameters.
1. A distributed optical sensing system, comprising:
a light source to generate light;
a waveguide positioned to optically interact with the light to produce backscattered light;
a compressive sampling filter positioned to selectively block portions of the light or the backscattered light based upon a compressive sampling technique; and
an optical receiver to receive the backscattered light.
2. A system as defined in claim 1 , wherein the compressive sampling filter is an optical switch or optical shutter.
3. A system as defined in claim 1 , wherein the compressive sampling filter is optically coupled between the waveguide and the optical receiver to selectively block portions of the backscattered light.
4. A system as defined in claim 1 , wherein the optical receiver has a bandwidth of 10 MHz or less.
5. A system as defined in claim 1 , wherein the compressive sampling filter is optically coupled between a local oscillator and a mixer to selectively block portions of the backscattered light.
6. A system as defined in claim 5 , wherein the mixer is a 90 degree hybrid mixer.
7. A system as defined in claim 5 , wherein the optical receiver is a balanced optical receiver.
8. A system as defined in claim 1 , wherein the compressive sampling filter is optically coupled between the light source and the waveguide to selectively block portions of the light.
9. A system as defined in claim 8 , wherein the light source generates a light pulse having width of 1 microsecond or longer.
10. A system as defined in claim 1 , further comprising processing circuitry communicably coupled to the receiver to receive the backscattered light and thereby determine a parameter being sensed by the waveguide.
11. A system as defined in claim 1 , wherein the waveguide is positioned along a wellbore.
12. A system as defined in claim 1 , wherein the waveguide is a fiber optic cable.
13. A distributed optical sensing method, comprising:
generating light that optically interacts with a waveguide to produce backscattered light;
selectively blocking portions of the light or the backscattered light using a compressive sampling filter; and
analyzing the backscattered light to thereby determine a parameter being sensed by the waveguide.
14. A method as defined in claim 13 , wherein selectively blocking the backscattered light comprises optically interacting the backscattered light with the compressive sampling filter.
15. A method as defined in claim 13 , wherein selectively blocking the backscattered light comprises using an optical switch or optical shutter to selectively block the backscattered light.
16. A method as defined in claim 13 , wherein selectively blocking the backscattered light comprises:
optically interacting a local oscillator light with the compressive sampling filter to produce a reference light;
optically interacting the reference and backscattered light with a mixer to produce mixed light; and
optically interacting the mixed light with the receiver to thereby generate the backscattered light.
17. A method as defined in claim 16 , wherein optically interacting the backscattered light further comprises phase shifting the reference light 90 degrees relative to the backscattered light.
18. A method as defined in claim 13 , wherein selectively blocking the backscattered light comprises optically interacting the light with the compressive sampling filter to produce a compressive sampling pulse having blocked regions.
19. A method as defined in claim 18 , wherein generating the light comprises generating a light having a pulse width of 1 microsecond or longer.
20. A method as defined in claim 13 , wherein determining the parameter comprises determining a parameter along a wellbore.
21. A distributed optical sensing method, comprising:
interrogating a sensing waveguide using an interrogation signal;
receiving backscattered signals from selected regions of the sensing waveguide based upon a compressive sampling technique; and
using the backscattered signals, determining a parameter being sensed by the sensing waveguide.
22. A method as defined in claim 21 , wherein receiving backscattered signals comprises selectively blocking portions of the backscattered signals using a compressive sampling filter positioned in-line with the sensing waveguide.
23. A method as defined in claim 21 , wherein receiving backscattered signals comprises selectively blocking portions of a local oscillator light.
24. A method as defined in claim 21 , wherein receiving backscattered signals comprises mixing the backscattered light with a reference signal.
25. A method as defined in claim 21 , wherein receiving backscattered signals comprises selectively blocking portions of the interrogation signal.
26. A method as defined in claim 21 , wherein a wellbore parameter is determined.