Abstract: A method of making a fiber optic accelerometer includes (a) drawing an optical fiber through a resin; (b) winding the resin coated fiber onto a disc mounted on an assembly having a central shaft; and (c) curing the resin-coated fiber. The optical fiber may be drawn through a resin by providing a container filled with a resin having an orifice therethrough and drawing the fiber through the orifice. The resin may be cured such that the fiber is bonded to the disc by curing the resin to the fiber and the disc at the same time.

Abstract: Methods for calibrating and making measurements using fiber optic sensors are disclosed using backscattered wavelengths and independent sensors. The disclosure sets outs methods applicable with fiber optic sensors either in a deployed in a loop and in a linear configuration and useful for measurements including temperature.

Abstract: High-resolution measurement of a parameter is provided at multiple different locations simultaneously along an optic fiber. Light within a predefined range of wavelengths is transmitted into an optic fiber that contains multiple birefringent fiber optic pressure transducers, each including a Fiber Bragg Grating. Each grating defines a spatially modulated index of refraction and a wavelength that is unique within the system. A sweeping comb filter is used to apply optical comb filtering to light reflected from the transducers so as to pass filtered light having multiple spectral portions, each spectral portion associated with one transducer. The free spectral range of the sweeping comb filter is set to be approximately equal to the spectral range of a single spectral portion. Wavelength division multiplexing is applied to the filtered light so as to separate the spectral portions.

Abstract: High-resolution measurement of a parameter is provided at multiple different locations simultaneously along an optic fiber. Light within a predefined range of wavelengths is transmitted into an optic fiber that contains multiple birefringent fiber optic pressure transducers, each including a Fiber Bragg Grating. Each grating defines a spatially modulated index of refraction and a wavelength that is unique within the system. A sweeping comb filter is used to apply optical comb filtering to light reflected from the transducers so as to pass filtered light having multiple spectral portions, each spectral portion associated with one transducer. The free spectral range of the sweeping comb filter is set to be approximately equal to the spectral range of a single spectral portion. Wavelength division multiplexing is applied to the filtered light so as to separate the spectral portions.

Abstract: A technique usable with a subterranean well includes deploying a first optical sensor downhole in the subterranean well. The technique includes observing an intensity of backscattered light from the first optical sensor to measure a distribution of a characteristic along a portion of the well. The technique includes deploying a second sensor downhole to measure the characteristic at discreet points within the portion. The second sensor is separate from this first sensor and includes at least one interferometric sensor.

Abstract: Methods for calibrating and making measurements using fiber optic sensors are disclosed using backscattered wavelengths and independent sensors. The disclosure sets outs methods applicable with fiber optic sensors either in a deployed in a loop and in a linear configuration and useful for measurements including temperature.

Abstract: A technique that usable in a subterranean well includes deploying a first sensor in a remote location to measure a distribution of a characteristic along a segment at the location. The technique includes deploying a second sensor downhole to measure the characteristic at discrete points within the segment. The second sensor is separate from the first sensor.

Abstract: High-resolution measurement of a parameter is provided at multiple different locations simultaneously along an optic fiber. Light within a predefined range of wavelengths is transmitted into an optic fiber that contains multiple transducers each formed as a grating. Each grating defines a spatially modulated index of refraction and a wavelength that is unique within the system. A Fabry-Perot Interferometer is used to apply optical comb filtering to light reflected from the transducers so as to pass filtered light having multiple spectral portions, each spectral portion associated with one transducer. The free spectral range of the Fabry-Perot Interferometer is set to be approximately equal to the spectral range of a single spectral portion. Wavelength division multiplexing is applied to the filtered light so as to separate the spectral portions. The value of a parameter is preferably determined using the spectral spacing of two maxima of spectral intensity in each spectral portion.

Abstract: Methods for enhancing dynamic range, sensitivity, accuracy, and resolution in fiber optic sensors include manipulating the polarization characteristics of the light entering a fiber optic sensor and/or manipulating the polarization characteristics of the light exiting the sensor before it enters the light detection system. An apparatus according to the invention includes a fiber optic core having one or more gratings written onto it, a light source and a detection system for detecting light transmitted through the grating or reflected by the grating. The light source and the spectral demodulation system may be coupled to opposite ends of the fiber optic (transmission mode) or may be coupled to the same end of the fiber optic through the use of a beam splitter and terminators (reflection mode). Apparatus according to the invention include a polarizer and controller located either between the light source and the fiber or between the fiber and the detection system.

Abstract: Methods and apparatus for measuring differential pressure with fiber optic sensor systems are disclosed. The apparatus of the present invention include both monopolar and bipolar sensors, sensors incorporating side-hole fibers, sensors incorporating fibers without side holes, FBGs subjected to transverse strain, and FBGs subjected to longitudinal strain. All of the embodiments utilize FBGs. Two embodiments utilize a piston having oppositely extending rods, each of which is exposed to a different pressure. Seven embodiments utilize one or more silica diaphragms coupled to a silica body and exposed to two pressures. In each of these embodiments, pressure is converted into movement of the piston or diaphragm which is then used to strain the FBG(s). When each FBG is interrogated, the spectral information is indicative of the strain exerted by the piston or diaphragm on the FBG and thus the difference between the two pressures.

Abstract: An optical fiber is provided with a Bragg grating formed along a portion of its core and a mechanical structure arranged adjacent to the Bragg grating for amplifying longitudinal strain on the fiber in the vicinity of the grating. The mechanical structure is designed to convert ambient pressure into longitudinal strain on the fiber in the vicinity of the grating and to allow the fiber to pass through the structure so that several pressure measuring apparatus may be arranged along a single optical fiber. An intermediate structure is provided between the fiber and the mechanical structure for minimizing buckling of the fiber. The methods of the invention include converting pressure into longitudinal strain on an optical fiber, amplifying the effect of pressure on the longitudinal strain, measuring pressure by determining the spectral location related to peaks (or minimums) of light reflected from an optical grating subjected to longitudinal strain.

Abstract: The apparatus of the present invention include an optical fiber with a Bragg grating formed along a portion of its core and a mechanical structure arranged adjacent to the Bragg grating for amplifying transverse strain on the fiber in the vicinity of the grating. In particular, the mechanical structure is designed to convert ambient pressure into transverse strain on the fiber in the vicinity of the grating. The methods of the invention include converting pressure into transverse strain on an optical fiber, amplifying the effect of pressure on the transverse strain, measuring pressure by determining the spacing between spectral locations related to peaks (or minimums) of light reflected from an optical grating subjected to transverse strain, and measuring the temperature of the grating by determining the locations of the spectral locations related to the peaks (or minimums) of light reflected from the grating.