Optoplan as

University of Southampton

Optomed. as

Optopian as

Jean-Luc Archambault

Laurence Reekie

David Neil Payne

Jon Thomas Kringlebotn

Audun Hordvik

Erlend Ronnekleiv

Hilde Nakstad

Arne Berg

Dag Thingbo

Ole Henrik Waagaard

Roar Furuhaug

Sverre Knudsen

Erlend Rønnekleiv

Reinold Ellingsen

Dag Roar Hjelme

Dag Thingb&oslash;

Jean Luc Archambault

Dag Roar Hjeime

Sigurd Weidemann L&oslash;vseth

Sigurd Weidemann Lovseth

The invention relates to a hydrophone housing. The housing comprises an outer casing with an exterior shape being in close contact with sediment when buried therein and having a deflectable wall part. Solid material partly fills the casing to define an outer chamber behind the deflectable wall part, a cavity shaped so that an inner chamber is defined immediately surrounding a hydrophone sensing element held therein, and a first duct for liquid flow communication between the outer chamber and the cavity or an internal volume of the hydrophone sensing element. Thereby, a hydraulic coupling is provided so that an acoustic pressure causing small radial displacements of outer surface of the housing will, via liquid in the first duct, cause large radial displacements of the hydrophone sensitive element. The area of the deflectable wall part is much larger than the area of the sensitive element so that only small displacements of the housing are required to cause large displacements at the hydrophone sensing element.

Hydrophone housing

There is provided a solid seismic streamer cable for use in seismic surveying in marine environments. The streamer is characterized by a buffer layerwhich is provided with a cut-outand a sensor element arranged in the cut-out. There is also provided an associated hydrophone for integration into the seismic streamer cable. The hydrophone is characteristic in a split-element sensor basebeing suited for efficient mounting into the cut-outsof the seismic cable. There is also provided an associated accelerometer for integration into the seismic streamer cable. The accelerometer is characteristic by a split-element sensor basefor being efficiently arranged into the cut-outsof the seismic cable. A method of producing a seismic streamer cable according to the invention incorporating a hydrophone or accelerometer according to the invention is also provided.

Method of producing a seismic streamer cable

There is provided a solid seismic streamer cable for use in seismic surveying in marine environments. The streamer is characterized by a buffer layerwhich is provided with a cut-outand a sensor element arranged in the cut-outThere is also provided an associated hydrophone for integration into the seismic streamer cable. The hydrophone is characteristic in a split-element sensor basebeing suited for efficient mounting into the cut-outsof the seismic cable. There is also provided an associated accelerometer for integration into the seismic streamer cable. The accelerometer is characteristic by a split-element sensor basefor being efficiently arranged into the cut-outsof the seismic cable. A method of producing a seismic streamer cable according to the invention incorporating a hydrophone or accelerometer according to the invention is also provided.

Split-element optical hydrophone

Seismic sensor systems and sensor station topologies, as well as corresponding cable and sensor station components, manufacturing and deployment techniques are provided. For some embodiments, networks of optical ocean bottom seismic (OBS) stations are provided, in which sensor stations are efficiently deployed in a modular fashion as series of array cable modules deployed along a multi-fiber cable.

Bi-directional interrogation of optical sensors

A seismic sensor station includes a housing containing a fiber optic hydrophone and a fiber optic accelerometer that can both be made from a single length of optical fiber arranged inside the housing. The fiber optic accelerometer is arranged in a liquid/oil filled compartment of the housing for dampening of mechanical resonances in the accelerometer due to mechanical disturbances and pressure fluctuations.

Seabed seismic station packaging

Devices and methods of accurately determining optical wavelengths, such as the Bragg wavelengths of an FBG sensor array. Wavelength-swept light having a characteristic spectrum is swept over a bandwidth and is applied to an interference filter. The interference filter produces an optical spectrum having one or more reference peaks that are identifiable because of the characteristic spectrum. The optical spectrum is converted into electrical signals having at least one electrical signal that is identifiable because of the characteristic spectrum. The identifiable electrical signal is used by a signal processor as an absolute, high accuracy wavelength reference. Temperature compensation or temperature stabilization can compensate the characteristic wavelength. Fiber Bragg sensor systems can use the wavelength reference to determine the Bragg wavelength of FBG elements. The characteristic spectrum can be imparted by the light source or an optical element such as a transmission line filter.

Wavelength reference system for optical measurements

Methods for coating an optical fiber with optical fiber Bragg grating (FBG) with a hermetic coating, particularly a coating of carbon, are employed to avoid ingress of gases, vapors or fluids in the ambient environment. This ingress can be from water or hydrogen, which can diffuse in the fiber glass and cause deviation/drift in the measured Bragg measurements. Bragg gratings that maintain the grating strength at temperatures in excess of 1000&#xb0; C. are used and can be formed by heating the fiber above 1000&#xb0; C. in a chamber with a reactive gas that produces deposition of carbon.

Method for preparing an optical fibre, optical fibre and use of such

An optical wavelength readout system for application in optical sensing systems is disclosed. The system includes a Master unit including a wavelength swept optical source for launching light into a string of optical sensors, and a detection and processing unit for detecting and processing the light emitted by the source. The system also includes a Slave unit including a light coupling device for coupling light from the light source into the string of sensors and for coupling light reflected from the string of sensors to a detection and processing unit arranged to detect and process the reflected light. The Master unit includes a wavelength reference unit adapted to make a reference signal available to other parts of the sensing system. The reference signal represents a generally exact relation between the wavelength of the light emitted from the source and time.

Optical wavelength interrogator

Fiber optic particle detector for measurements in a fluid flow, comprising an optical fiber () being acoustically coupled to a mechanical element () adapted to be acoustically coupled to the flow, a fiber optic interferometer () and a light source () providing light in said optical fiber.

Apparatus for acoustic detection of particles in a flow using a fiber optic interferometer

A body compatible fiber optic sensor probe for invasive medical use is provided. The probe includes at least one sensing location at which the fiber is configured to provide at least one detectable changeable optical property responsive to strain within the fiber, and at least one sensing element which undergoes a volumetric change in response to an in body parameter to be sensed. The sensing element is coupled to the fiber in such a way that the volumetric change induces strain within the fiber so as to vary the detectable optical property or properties.

Fiber optic probes

A fiber optic sensor system comprises at least one measuring sensorproviding an optical output dependent upon one or more parameters to be measured, e.g. temperature, and at least one reference sensorproviding a reference output for comparison with the measuring sensor output. The reference sensor is provided in a birefringent fiber. The system includes a detecting meanswhereby a reference beat signal fis derived by measuring the optical frequency splitting between frequency components in different polarization planes of the reference sensor output. A further beat signal fis generated between the measuring and reference sensor outputs, such beat signals being used to derive a measurement of one or more parameters.

Fiber optic sensing systems and method of use thereof

A method for measurements of the orthogonally polarized minimum and maximum Bragg wavelengths of one of several birefringent fiber Bragg grate FBG sensors, and alternatively a method for eliminating errors in FBG sensor measurements caused by undesired grating birefringence, using an FBG wavelength interrogation apparatus, where the light from a polarized wavelength swept narrowband source ( ) is passed through an electrically controllable polarization controller ( ), operated in either a scanning mode or a tracking mode to find the two orthogonally polarized reflection spectra of the birefringent FBGs ( ) with corresponding minimum and maximum Bragg wavelength &ggr; and &ggr; , where a low-birefringent reference FBG with known wavelength ( ) and a low-birefringent fixed Fabry-Perod interferometer ( ), generating frequency equidistant peaks are used in combination to provide accurate and readable wavelength measurements.

Method and apparatus for interrogation of birefringent FBG sensors

A Bragg Grating optical waveguide laser source comprising at least one Bragg grating in a rare earth doped waveguide and an optical pump source coupled to said doped waveguide, said Bragg gratings having at least two different peak reflection wavelengths and at least one of said Bragg gratings comprising a phase-shift and a phase-shift actuator being coupled to the phase-shift for controlled application of changes in the phase-shift thus activating or deactivating the corresponding Bragg grating waveguide laser.

Waveguide laser source

Fibre optic apparatus for accurate and repeatable measurements of light comprising one or more wavelength ranges, and system employing the apparatus. The apparatus according to the invention comprises: a directional coupler adapted to lead the light into an optical fibre, said optical fibre containing at least one analysis filter for each wavelength range, said analysis filters consisting of at least one fibre-optical Bragg-grating (FBG) which reflects incident light with a chosen wavelength back through said directional coupler and onto a detector having an associated signal processing unit, a modulator device for pulsing the incident light with a chosen pulse width, and an optical fibre delay line in front of each analysis filter, with a length adapted to provide for a sufficient time delay larger than the pulse width, so that the pulses reflected from each analysis filter at different wavelengths can be separated in time and thereby be demodulated in the signal processing unit.

Growing community of inventors

Trondheim, Norway

Jon Thomas Kringlebotn