公开(公告)号：US20180245957A1

公开(公告)日：2018-08-30

申请号：US15962196

申请日：2018-04-25

Applicant: SILIXA LTD. ,  CHEVRON USA INC.

Inventor： Mahmoud Farhadiroushan ,  Daniel Finfer ,  Veronique Mahue ,  Tom Parker ,  Sergey Shatalin ,  Dmitry Strusevich

IPC: G01F1/66 ,  G02B6/44 ,  G01D5/353

Abstract: Embodiments of the present invention provide a cable for optical fiber sensing applications formed from fiber wound around a cable core. A protective layer is then preferably placed over the top of the wound fiber, to protect the fiber, and to help keep it in place on the cable core. The cable core is preferably of a diameter to allow bend-insensitive fiber to be wound thereon with low bending losses. The effect of winding the fiber onto the cable core means that the longitudinal sensing resolution of the resulting cable is higher than simple straight fiber, when the cable is used with an optical fiber sensing system such as a DAS or DTS system. The achieved resolution for the resulting cable is a function of the fiber winding diameter and pitch, with a larger diameter and reduced winding pitch giving a higher longitudinal sensing resolution.

公开(公告)号：US20180045543A1

公开(公告)日：2018-02-15

申请号：US15555628

申请日：2016-03-07

Applicant: Silixa Ltd.

Inventor： Mahmoud Farhadiroushan ,  Tom Parker ,  Sergey Shatalin

IPC: G01D5/353 ,  G01H9/00

CPC classification number: G01D5/35374 ,  G01D5/35306 ,  G01D5/3537 ,  G01H9/004

Abstract: An optical fiber distributed acoustic sensor system includes weak broadband reflectors inserted periodically along the fiber. The reflectors reflect only a small proportion of the light from the DAS incident thereon back along the fiber, typically in the region of 0.001% to 0.1%, but preferably around 0.01% reflectivity per reflector. In addition, to allow for temperate compensation to ensure that the same reflectivity is obtained if the temperature changes, the reflection bandwidth is relatively broadband. In some embodiments the reflectors are formed from a series of fiber Bragg gratings, each with a different center reflecting frequency, the reflecting frequencies and bandwidths of the gratings being selected to provide the broadband reflection. A chirped grating may also be used to provide the same effect. In preferred embodiments, the reflectors are spaced at half the gauge length i.e. the desired spatial resolution of the optical fiber DAS.