Abstract: A method is disclosed for marine seismic surveying in which upgoing and downgoing components of a seismic wavefield at a seafloor location, and the seismic wavefield at a seismic streamer location substantially above the seafloor location are determined. The upgoing and downgoing seafloor components and the streamer seismic wavefield are used to determine a separation operator. The separation operator when applied to the streamer seismic wavefield provides an estimate of at least one of an upgoing wavefield component and a downgoing wavefield component of the determined seismic wavefield for the streamer location.

Abstract: Seismic prospecting method and device using simultaneous emission of seismic signals obtained by coding a signal by pseudo-random sequences, and notably a periodic signal phase modulated by such sequences. Signals such as, for example, periodic signals phase modulated according to a pseudo-random code (binary for example), produced by a control unit, are for example emitted in the ground by means of vibrators, the seismic signals reflected by the subsoil discontinuities in response to the periodic signals emitted are picked up by receivers coupled with the formation and recorded in an acquisition and recording system. The periodic signals are emitted simultaneously by the vibrators.

Abstract: The meters of coiled silica fiber in conventional R-EDFAs is replaced with an ultra-short high-gain waveguides formed of co-doped erbium-ytterbium multi-component glass a few centimeters in length. The compact R-EDA is pumped using non-conventional multi-mode pumps that couple to the waveguide cladding. The multi-component glasses support doping concentrations of the rare-earth ions erbium and ytterbium far in excess of levels believed possible with conventional glasses. These dopant levels in combination with the reflective scheme make a compact R-EDA with sufficient amplification possible.

Abstract: A Raman optical amplifier for amplifying an optical signal propagating in an optical fiber associated with an optical communications system. The amplifier includes a first Raman pump source including a first pump laser coupled to the fiber to provide first order Raman pump light for amplifying the optical signal, and a second Raman pump source including a second pump laser coupled to the fiber to provide second order Raman pump light for amplifying the first order Raman pump light. The first and second order Raman pump light is introduced into the fiber in either a co-propagating or counter-propagating direction relative to the propagation direction of the optical signal in the fiber. The second pump laser may include first and second pump laser elements that generate the second order Raman pump light, where a center wavelength of the light generated by the first laser element is different than the center wavelength of the light generated by the second laser element.

Abstract: An optical amplifier comprises: (i) an input port for providing optical signal to the amplifier; (ii) an output port for providing amplified optical signal out of the amplifier; (iii) at least two optical fibers, one optical fiber having positive dispersion D1 of greater than 10 ps/nm/km in a 1550 nm to 1620 nm wavelength range, the other fiber having negative dispersion D2 of less than −5 ps/nm/km in a 1550 nm to 1620 nm wavelength range, wherein the length of each of said optical fiber is chosen to provide the amplifier with a predetermined amount of dispersion.

Abstract: A method of broadband amplification divides an optical signal of wavelength of 1430 nm to 1620 nm at a preselected wavelength into a first beam and a second beam. The first beam is directed to at least one optical amplifier and produces an amplified first beam. The second beam is directed to at least one rare earth doped fiber amplifier to produce an amplified second beam. The first and second amplified beams are combined.

Abstract: A broadband nonlinear polarization amplifier includes an input port for inputting an optical signal having a wavelength &lgr;. A distributed gain medium receives and amplifiers the optical signal through nonlinear polarization. The distributed gain medium has zero-dispersion at wavelength &lgr;0. A magnitude of dispersion at &lgr; is less than 50 ps/nm-km. One or more semiconductor lasers are operated at wavelengths &lgr;p for generating a pump light to pump the distributed gain medium. An output port outputs the amplified optical signal.

Abstract: A double pumped Raman amplifier is provided that increases gain over a same length of gain fiber without significantly increasing a percentage of noise. The amplifier may include a source of pump light coupled to the output end of a coil of Raman gain fiber, and a reflector coupled to the input end of the coil which may be either a mirror, or a fiber Bragg grating. Alternatively, a beam splitter may be connected to the source of pump light and the resulting split output may be coupled to both the input and output ends of the gain fiber. The increase in amplification efficiency allows the optical fiber used in components such as dispersion compensating modules to also be used as Raman gain fiber in such amplifiers.

Abstract: According to an illustrative embodiment of the present invention, a method for controlling an optical amplifier is disclosed. The illustrative method includes receiving a portion of an input signal to the optical amplifier; receiving a portion of an output signal from a first amplification stage; receiving a portion of an output signal of the optical amplifier; and adjusting the first amplification stage and a second amplification stage based on the received portions to substantially control the optical amplifier. According to another illustrative embodiment of the present invention, an optical amplifier includes a controller which receives a portion of an output signal from a first amplification stage and a portion of an output signal from the optical amplifier. The controller adjusts the first amplification stage and a second amplification stage based on the received portions of the signals.

Abstract: The invention relates to an optical fiber amplifier device with an optical signal input and output with first piece of amplifying fiber doped with lanthanide in a double-clad structure, a second piece of amplifying fiber doped with lanthanide in a ring structure and lasers for pumping the two fiber pieces with at least one pump module.

Abstract: A variable gain optical amplifier and method for control thereof is provided that includes an amplifier stage having a light pump, and a power source for the pump, and a variable optical attenuator connected to the amplifier stage and having a movable controller that changes attenuation of the amplifier output when moved to a different position. The dynamic controller of the amplifier includes gain detecting circuits that generate signals indicative of input and output signal strengths of the amplifier stage, and a circuit that provides a signal indicative of a position of the attenuator controller, as well as a digital signal processor connected to the outputs of the gain detecting circuits and position indicating circuit. The digital process maintains a selected gain setpoint for the amplifier in accordance with a predetermined relationship between amplifier gain and the signal input and output strengths, and a position of the attenuator controller and signal attenuation.

Abstract: The invention is a method for removing trapped water bottom multiples, receiver side peg-leg multiples, and source side peg-leg multiples from dual sensor OBC data, where the data includes both pressure signals and velocity signals. The pressure and velocity signals are compared to determine any polarity reversals between them. Polarity reversals are used to identify and separate up-going and down-going wavefields in the pressure and velocity signals. A matching filter is applied to a portion of the velocity signal where polarity reversals exist. The down-going wavefield is then estimated by calculating the difference between the portion of the velocity signal where polarity reversals exist and the portion of the pressure signal where polarity reversals exist and applying a scaling factor to the result. An attenuated up-going pressure wavefield is then determined by combining the estimated down-going wavefield and the pressure signal.

Abstract: A method for analyzing and classifying the morphology of seismic objects extracted from a 3D seismic data volume. Any technique may be used to extract the seismic objects from the 3D seismic data volume. According to the inventive method, one or more morphologic parameters are selected for use in classifying the morphology of the selected seismic objects. Geometric analyses are then performed on each seismic object to determine geometric statistics corresponding to the selected morphologic parameters. The results of these geometric analyses are used to classify the morphology of the seismic objects according to the selected morphologic parameters.

Abstract: Optical automatic gain control (AGC) is accomplished using stable, non-absorbing optical hard limiters and various optical logic gates derived therefrom. The AGC mechanism preserves the ratios between signal levels and provides an adjustable amount of gain.

Abstract: An optical amplifier includes an optical amplifying medium having a multiplexed light input thereto and providing an output of amplified multiplexed light, an excitation source which excites the optical amplifying medium; and at least one of a first monitor for monitoring the amplified multiplexed light from the optical amplifying medium and a second monitor for monitoring the multiplexed light input to the optical amplifying medium. An operation amount of the excitation source for the optical amplifying medium is controlled using a monitoring result output from at least one of said first and second monitors.

Abstract: A sonic logging tool that can be positioned within a fluid-filled borehole includes an axially distributed active vibration control system to reduce tool borne noise. The tool includes an acoustic transmitter, an axial array of acoustic receivers, and actuator assemblies that are coupled to cancel tool mode vibrations at stations along the receiver section of the tool. In a preferred embodiment, force is applied in feedback mode based on tool mode vibrations sensed at each station. The force at each station is applied by a real-time computational algorithm using feedback. The feedback includes weighting to accommodate monopole or dipole tool mode vibration. The computational algorithm includes FIR processing of signals received from a vibration sensor assembly. The force applied at a given station is a function of tool mode vibration measured at that station and the predetermined values of a set of FIR filter coefficients associated with the given station.

Abstract: An optical amplifier for two adjacent bands of optical data channels provides gain across the entire spectrum, including the so-called dead-band, by splitting the entire input signal equally into two paths. One path is optimized to amplify one band and the other path is optimized to amplify the other. An optical delay in one path, usually the one optimized for the lower wavelength band, ensures equal optical path lengths for the two paths. The amplified signals in that two paths are then combined to yield or flat gain profile across the two bands and the gap in-between.

Abstract: A hybrid optical signal amplifier is provided which includes the combination of a Raman amplifier and an EDFA assembly. The Raman amplifier has an output defined by regions of higher and lower gain levels, and the EDFA assembly has an output having a region, near the longer wavelengths thereof, that includes a maximum noise figure. The spectrum region of higher gain level of the Raman amplifier is selected to correspond to the spectrum region of the EDFA assembly that includes the maximum noise figure in order to lower the maximum noise figure of the resulting optical signal amplifier, as well as to flatten the gain across the output spectrum.

Abstract: An acoustic tool that provides a programmable source waveform is disclosed. Numerous advantages may be achieved from the configurability of the source waveform. Notably, acoustic logs at multiple frequencies may be acquired with a single pass. The waveform may be frequency-adapted to maximize formation response and amplitude adapted for gain control. In one embodiment, the acoustic tool comprises: a controller, a digital-to-analog controller (DAC), an acoustic transducer, and a linear driver. The DAC converts a digital waveform from the controller into an analog waveform. The acoustic transducer converts an electrical signal into an acoustic signal. The linear driver receives the analog waveform from the DAC and responsively provides the electrical signal to the acoustic transducer. The electrical signal is proportional to the analog waveform. The tool may further include a memory for storing the digital waveform and/or software for generating the digital waveform.

Abstract: A modular interleaved Raman amplifier structure is exploited to reap the advantages provided by the high Raman gain coefficient and small effective area of highly nonlinear fibers without incurring penalties caused by nonlinear effects and double-Rayleigh backscattering noise. Very tight WDM channel spacings may be accommodated. The amplifier structure may be implemented at very low initial cost and with high reliability, scalability, and modularity.