The present invention relates to a bend stiffener comprising a first elongate member (1) having a longitudinal conduit (2) and a second elongate member (3) having also a longitudinal conduit (4) being connected to an end (5) of said first member (1) thereby effectively extending the compound length of the bend stiffener, the first member (1) having a chosen resilience in order to be able to bend properly when the bend stiffener is subject to a certain load, i.e. at a large tension and small angle, while the second member (3) is designed so as to have less resilience than said first member, whereby the second member typically will start bending earlier than said first member when the bend stiffener is subjected to a smaller load, i.e. at a low tension and/or a large angle. The first and second members are preferably provided with one or more channels (7,18, 16, 8) from the second member 3 to the hydrophone 10, the channel surfaces having a nonmetallic material, e.g. a polymer, the second member having a resilience being adapted to transfer incident pressure waves into said channel (18) therein.
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.
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.
Storage and installation systems used in storage, deployment or retrieval of a seismic cable array include one or more baskets adapted for being stacked. Each basket is dimensioned to allocate, in an ordered arrangement, a number of seismic stations interconnected by sections of seismic cable. Corresponding methods of storing a seismic cable and deploying/retrieving a seismic cable are based on the use of baskets having an ordered arrangement of seismic stations.
Unwanted signal components in time-division multiplexed (TDM) systems may lead to crosstalk and noise if these pulses overlap with signal pulses from an interrogated sensor. The crosstalk and noise are dominated by interference between the signal pulses from the interrogated sensor and the unwanted signal components and can be greatly reduced by suppressing this interference signal. The unwanted signal components may include overlapping pulses originating from different sets of interrogation pulses (repetition periods). Modulating the phase or frequency between the repetition periods so that the unwanted interference signal does not appear at frequencies from which the phase of the interrogated sensor is demodulated suppresses this interference. Other unwanted signal components include leakage light during dark periods of the duty cycle of an interrogation signal. Modulating the phase difference between the interrogation signal and the leakage light suppresses the interference between the leakage light and the interrogation signal.
G08C 15/12 - Dispositions caractérisées par l'utilisation du multiplexage pour la transmission de plusieurs signaux par une voie commune successivement, c. à d. utilisant la division de temps les signaux étant représentés par des caractéristiques d'impulsion dans la voie de transmission
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G08C 23/04 - Systèmes de transmission de signaux non électriques, p.ex. systèmes optiques utilisant des ondes lumineuses, p.ex. infrarouges
H04J 3/10 - Dispositions pour reduire la diaphonie entre canaux
H04J 14/08 - Systèmes multiplex à division de temps
6.
METHOD AND APPARATUS FOR SUPPRESSION OF CROSSTALK AND NOISE IN TIME-DIVISION MULTIPLEXED INTERFEROMETRIC SENSOR SYSTEMS
Unwanted signal components in time-division multiplexed (TDM) systems may lead to crosstalk and noise if these pulses overlap with signal pulses from an interrogated sensor. The crosstalk and noise are dominated by interference between the signal pulses from the interrogated sensor and the unwanted signal components and can be greatly reduced by suppressing this interference signal. The unwanted signal components may include overlapping pulses originating from different sets of interrogation pulses (repetition periods). Modulating the phase or frequency between the repetition periods so that the unwanted interference signal does not appear at frequencies from which the phase of the interrogated sensor is demodulated suppresses this interference. Other unwanted signal components include leakage light during dark periods of the duty cycle of an interrogation signal. Modulating the phase difference between the interrogation signal and the leakage light suppresses the interference between the leakage light and the interrogation signal.
G01D 5/32 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux
G01D 5/36 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques formant la lumière en impulsions
G08C 15/12 - Dispositions caractérisées par l'utilisation du multiplexage pour la transmission de plusieurs signaux par une voie commune successivement, c. à d. utilisant la division de temps les signaux étant représentés par des caractéristiques d'impulsion dans la voie de transmission
G08C 23/06 - Systèmes de transmission de signaux non électriques, p.ex. systèmes optiques utilisant des ondes lumineuses, p.ex. infrarouges à travers des guides de lumière, p.ex. des fibres optiques
7.
METHOD AND APPARATUS FOR SUPPRESSION OF CROSSTALK AND NOISE IN TIME-DIVISION MULTIPLEXED INTERFEROMETRIC SENSOR SYSTEMS
Unwanted signal components in time-division multiplexed (TDM) systems may lead to crosstalk and noise if these pulses overlap with signal pulses from an interrogated sensor. The crosstalk and noise are dominated by interference between the signal pulses from the interrogated sensor and the unwanted signal components and can be greatly reduced by suppressing this interference signal. The unwanted signal components may include overlapping pulses originating from different sets of interrogation pulses (repetition periods). Modulating the phase or frequency between the repetition periods so that the unwanted interference signal does not appear at frequencies from which the phase of the interrogated sensor is demodulated suppresses this interference. Other unwanted signal components include leakage light during dark periods of the duty cycle of an interrogation signal. Modulating the phase difference between the interrogation signal and the leakage light suppresses the interference between the leakage light and the interrogation signal.
G01D 5/26 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette
Accelerometers for determining acceleration and methods of fabricating an accelerometer are disclosed. In one embodiment, the accelerometer includes a frame, a mass movably suspended on the frame, a fixed element having a rounded surface that does not move with respect to the frame, a movable element having a rounded surface that moves with the mass, and a sensing coil of optical waveguide wrapped around the rounded surfaces to detect movement of the mass in response to acceleration based on interferometric sensing of a change in length of the sensing coil. A method of fabricating the accelerometer includes suspending the mass in the frame and wrapping the optical waveguide around the rounded surfaces. Sensitivity and low fabrication cost of the accelerometers enables their use for integration within an ocean bottom seismic cable. Further, the accelerometer may be an in-line or a cross- line accelerometer depending on the arrangement within the frame.
G01P 15/02 - Mesure de l'accélération; Mesure de la décélération; Mesure des chocs, c. à d. d'une variation brusque de l'accélération en ayant recours aux forces d'inertie
G01P 15/03 - Mesure de l'accélération; Mesure de la décélération; Mesure des chocs, c. à d. d'une variation brusque de l'accélération en ayant recours aux forces d'inertie en utilisant des moyens non électriques
G01P 15/093 - Mesure de l'accélération; Mesure de la décélération; Mesure des chocs, c. à d. d'une variation brusque de l'accélération en ayant recours aux forces d'inertie avec conversion en valeurs électriques ou magnétiques au moyen de capteurs photo-électriques
Methods and apparatus for cable termination and sensor integration at a sensor station within an ocean bottom seismic (OBS) cable array are disclosed. The sensor stations include a housing for various sensor components. Additionally, the sensor stations can accommodate an excess length of any data transmission members which may not be cut at the sensor station while enabling connection of one or more cut data transmission members with the sensor components. The sensor stations further manage any strength elements of the cable array.
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.
A method for interrogating time-multiplexed interferometric sensors using multiple interrogation pulses so as to increases the allowable interrogation pulse duty-cycle and improve the signal-to-noise ratio. In each TDM repetition period a sequence of multiple interrogation pulses are generated. The pulses in the sequence are separated by a time that is equal to the sensor imbalance. The phase from pulse to pulse in each TDM time-slot is modulated at a different, linear rate such that the pulse in time-slot m will have an optical frequency that is shifted by m.DELTA..nu., where .DELTA..nu. is the sub-carrier frequency. Because multiple reflections do not need to fade out the inventive method can enhance the signal-to-noise ratio of interferometric sensors such as inline Fabry-Perot sensors.
G01D 5/26 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette
12.
WAVELENGTH REFERENCE SYSTEM FOR OPTICAL MEASUREMENTS
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.
Methods and apparatus for reducing the coherence of an optical signal that is used to interrogate optical interferometric sensors are disclosed. The optical field phasor of the interrogation source is modulated in a controlled manner to produce a broadened optical source power spectrum at the output of the source unit. The output from the source unit is launched into an optical sensor network, comprising a multiple of optical pathways from its input to the detection unit, where pairs of optical pathways form sensor interferometers. A compensating interferometer with delay difference similar to the sensor delay difference may be arranged in a serially coupled manner with the optical sensor network, either before or after the network. The optical output power from the source unit may either be continuous or pulsed with a pulse duration similar to the sensor delay. The coherence modulation may be performed through direct modulation of the source or through external modulation of the light with piezoelectric ring modulator, a Lithium niobate phase or intensity modulator, or an acoustooptic modulator.
G01J 9/02 - Mesure du déphasage des rayons lumineux; Recherche du degré de cohérence; Mesure de la longueur d'onde des rayons lumineux par des méthodes interférométriques
G01D 5/26 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
G01H 9/00 - Mesure des vibrations mécaniques ou des ondes ultrasonores, sonores ou infrasonores en utilisant des moyens sensibles aux radiations, p.ex. des moyens optiques
G01L 11/02 - Mesure de la pression permanente, ou quasi permanente d'un fluide ou d'un matériau solide fluent par des moyens non prévus dans les groupes ou par des moyens optiques
14.
METHOD AND APPARATUS FOR REDUCING CROSSTALK INTERFERENCE IN AN INLINE FABRY-PEROT SENSOR ARRAY
A method and apparatus for reducing crosstalk between sensors in an inline Fabry-Perot (FP) sensor array. The inline FP sensor array comprises a plurality of fiber Bragg gratings arranged periodically along an optical fiber. The sensors are formed between each of the Bragg gratings. A light source provides multiplexed pulses as interrogation pulses for the array. The light pulses are applied to one end of the sensor array and a light detector detects reflected pulses. The detected pulses comprise a composite of reflections from all the Bragg gratings along the fiber. The apparatus processes the detected signals using an inverse scattering algorithm to detect an accurate phase response from each of the Bragg sensors while reducing crosstalk from other Bragg sensors within the array. One form of inverse scattering algorithm is a layer-peeling algorithm.
G01D 5/353 - Moyens mécaniques pour le transfert de la grandeur de sortie d'un organe sensible; Moyens pour convertir la grandeur de sortie d'un organe sensible en une autre variable, lorsque la forme ou la nature de l'organe sensible n'imposent pas un moyen de conversion déterminé; Transducteurs non spécialement adaptés à une variable particulière utilisant des moyens optiques, c. à d. utilisant de la lumière infrarouge, visible ou ultraviolette avec atténuation ou obturation complète ou partielle des rayons lumineux les rayons lumineux étant détectés par des cellules photo-électriques en modifiant les caractéristiques de transmission d'une fibre optique
brevets
