Stationary system for the active and/or passive monitoring of an underground deposit

A system and method for signal distribution within a sensor array uses a coaxial transmission line. Taps are affixed to the outer conductor of the coaxial transmission line and include field coupling portions extending into the internal field region of the coaxial transmission line. Electromagnetic energy propagating within the transmission line can be extracted to power the sensors. Sensor signals can be modulated onto radio frequency signals and propagated along the transmission line to distribute the sensor signals.

Sonar sensor array signal distribution system and method

A pair of connectors that convert electrical signals into optical signals for transmission along an optic fiber, and that also convert optical signals received from an optic fiber into electrical signals, is combined with a two-optic-fiber cable to provide an interconnecting cable assembly that receives electrical signals from a sending apparatus at either end of the cable, and presents electrical signals to a receiving apparatus at the other end of the cable, although the intervening transmission is optical. One optic fiber optically links the electrical-to-optical converter (light emitter) in one connector to the optical-to-electrical converter (light detector) in the second connector, while the other optic fiber optically links the emitter in the second connector to the detector in the first connector; thus the cable assembly is bidirectional and may be laid down and connected in either orientation with equivalent performance. Preamplification and buffering is provided within each connector, for the optical-to-electrical conversion. Simple, easy to use, but very accurate alignment devices for juxtaposing the optical fibers to the sources and detectors permit rapid but reliable replacement of the cable. Such cable assemblies are advantageous in collecting data for seismic geomapping for petroleum, particularly when electrical wires too are in the cable assembly.

Bidirectional optical electronic converting connector with integral preamplification

Embodiments of fiber optic communication systems are disclosed. In one embodiment, the system includes an optical channel having a channel response, a pulse-shaping transmitter coupled to a first end of the optical channel, and a receiver coupled to a second end of the optical channel. The transmitter includes a spread pulse modulator to shape pulses of data prior to transmission and an electrical to optical converter to transmit electrical data signals as the light signals over the optical channel. The receiver includes an optical to electrical converter to receive light signals from the optical channel and generate electrical data signals and a matched filter to receive and filter the electrical data signals with a response substantially matching a combined response of the transmitter and the channel response to increase a signal to noise ratio thereof.

Systems with spread-pulse modulation and nonlinear time domain equalization for fiber optic communication channels

A synchronous read channel having a single chip integrated circuit digital portion which provides digital gain control, timing recovery, equalization, digital peak detection, sequence detection, RLL(1,7) encoding and decoding, error-tolerant synchronization and channel quality measurement is disclosed. The integrated circuit accommodates both center sampling and side sampling, and has a high degree of programmability of various pulse shaping and recovery parameters and the ability to provide decoded data using sequence detection or digital peak detection. These characteristics, together with the error-tolerant sync mark detection and the ability to recover data when the sync mark is obliterated, allow a wide variety of retry and recovery strategies to maximize the possibility of data recovery. Various embodiments, including an embodiment incorporating the analog functions as well as the primary digital functions of the read channel in a single integrated circuit, and preferred embodiments utilizing a reduced complexity, programmable modified Viterbi detector supporting a broad class of partial response channels are disclosed.

Synchronous read channel

An optical fiber cable is used as the transmission medium for data and status signals from remote digital acquisition units to a master station of a distributed digital field system. Each digital acquisition unit has associated with it one or more sensors for sensing motion in an elastic body. The master station of the system also uses an optical fiber cable as the transmission medium for transmitting command signals to the digital acquisition units. The digital acquisition units, when first connected into the system, sense the master station signal and determine which direction to transmit. In normal operation, one digital acquisition unit receives the master station command and repeats the command to the next digital acquisition unit and so on. The digital acquisition units then reverse direction of transmission and reception, the data acquisition unit receiving from an adjacent digital acquisition unit and repeating data or status signals, then adding its own data or status signal onto the line before passing it to the next digital acquisition unit in the direction of the master station. The optical fiber cable transmission medium provides extremely high bandwidths permitting very high data rates and large numbers of channels and also provides complete immunity from electromagnetic radiation.

Optical transmission of digital seismic data

This disclosure relates to dc removal in data systems and in particular to multichannel, multiplexed data, gain ranging, seismic data acquisition systems. A medium drift dc amplifier (approximately + OR - 2.5 Mu v/*C) replaces the chopper stabilized amplifier. An overrange capability is provided in both the A/D converter and the gain ranging amplifier so the combined drift of the medium drift amplifier and the gain ranging amplifier over the system temperature is less than the overrange. This eliminates the necessity for rezeroing as the temperature changes or from using part of the converter range for dc drift. The digital filter has at least one word of memory per input channel plus one for each gain of the gain ranging amplifier. The input of the gain ranging amplifier is shorted periodically by Switch S and the average dc offset for each gain of the gain ranging amplifier is accumulated by filtering. An average is also accumulated by filtering for each of the data channels while they are in normal operation. Two cascaded one pole filters which share common hardware are used. The first removes the portion of offset due to the gain ranging amplifier and the second removes the dc offset due to the stabilized amplifier and multiplexer.

Digital dc offset removal method for data systems

Balanced drive for semiconductor diode attenuator in automatic gain controlled amplifier

A geophysical data acquisition system is disclosed having a dynamic range larger than that achievable with typical existing systems. The range of input signals that can be accommodated by a system are limited on the lower end by the noise level of the system and at the upper end by saturation levels of the system. High amplitude input signals can be accommodated by the system if certain unneeded frequency components are filtered off at a sufficiently early point in the signal flow path. In the present invention this desirable filtering is accomplished while maintaining a high gain level in the signal flow path ahead of those components which introduce high noise levels. As a result, the system has an expanded dynamic range and the needed capability to faithfully acquire low amplitude signals.

Ralph A. Harris

Papers

Optical transmission of digital seismic data

Digital dc offset removal method for data systems

Balanced drive for semiconductor diode attenuator in automatic gain controlled amplifier

Method and apparatus for increasing the dynamic range of a data acquisition system at low frequencies without reducing high frequency gain

Amplifying system having high speed and high accuracy gain control