Litton Systems, Inc.

Leland Stanford Junior University

Intel Corporation

Northrop Grumman Systems Corporation

Craig W Hodgson

Donald A Frederick

Jefferson L Wagener

H John Shaw

Michel J Digonnet

Michel J F Digonnet

Eric Lee Goldner

Dario G Falquier

William Christopher Knaack

John A Roscigno

Housings for use in optical packages, optical packages, and methods to manufacture the same are disclosed. A disclosed optical assembly includes a housing having a ferrule to receive an optical fiber; a lens; an annular mechanical interface; and a total internal reflection surface disposed between the ferrule and the lens to direct light between the ferrule and the lens. The example optical package also includes an optical element coupled to the mechanical interface of the housing to form a sealed chamber. The lens is disposed within the sealed chamber substantially in optical alignment with the optical element.

Optical packages and methods to manufacture the same

Sensor arrays utilizing standard 1&#xd7;2 couplers reduce the differences in the returned optical power levels by appropriate selection of the coupling ratios. Preferred embodiments are described that comprise 6 distribution fiber lines and 16 return fiber lines. One embodiment includes 16 sensor groups in which each sensor group has a dedicated return line. In another embodiment, 8 sensor groups are configured so that no two adjacent sensors have either a common distribution fiber line or a common return fiber line.

Architecture for large optical fiber array using standard 1&#xd7;2 couplers

Sensor arrays utilizing standard 1&times;2 couplers reduce the differences in the returned optical power levels by appropriate selection of the coupling ratios. Preferred embodiments are described that comprise 6 distribution fiber lines and 16 return fiber lines. One embodiment includes 16 sensor groups in which each sensor group has a dedicated return line. In another embodiment, 8 sensor groups are configured so that no two adjacent sensors have either a common distribution fiber line or a common return fiber line.

Architecture for large optical fiber array using standard 1&times;2 couplers

A system for sensing subterranean acoustic waves emitted from an acoustic source includes a plurality of laser sources, a plurality of subterranean optical sensors, at least one optical detector, and electronics. The laser sources each emit light at a different frequency. The subterranean optical sensors receive the light and alter the light in response to the acoustic waves. The optical detector receives the altered light and outputs an electrical signal. The electronics receives the electrical signal and converts it into seismic data format. The hydrophone for sensing the acoustic signals is able to operate at pressures of at least 5,000 psi and temperatures of at least 130 degrees Celsius. A hydrophone may be housed in a cable having a diameter of less than about 1.5 inches. The hydrophone's sensor preferably includes a reference mandrel, two sensing mandrels, and a telemetry can, all of which are aligned in a coaxial, end-to-end configuration to reduce the profile of the hydrophone. Flexible interlinks having grooves therein for receiving optical fiber join the mandrels together. The reference mandrel and sensing mandrels advantageously have hemispherically-shaped endcaps, permitting them to operate at high pressure.

Acoustic sensing system for downhole seismic applications utilizing an array of fiber optic sensors

An optical sensor architecture receives an input optical signal from a signal source and outputs a perturbed optical signal from at least one sensor to a receiver. An optical amplifier is positioned along a return fiber at an optical distance at least 10 kilometers from the receiver, with the optical amplifier amplifying the perturbed optical signal propagating to the receiver. If only one optical amplifier is used, the optical distance between the amplifier and the receiver may be between about 10 km and about 80 km, and an optical distance of between about 10 km and about 150 km may separate the sensor and the receiver. If additional optical amplifiers and dedicated pump distribution fibers are used, the optical distances may be correspondingly greater. Alternatively, increasing the number of sensors necessitates a reduction in the optical distance separating the sensors from shore.

Long distance, all-optical telemetry for fiber optic sensor using remote optically pumped EDFAs

The present invention significantly improves the signal to noise ratio (SNR) in a passive optical array comprising sensors located in rungs between a distribution bus and a return bus. Erbium-doped optical fiber amplifiers are included in the buses proximate to each rung coupling to offset the coupler splitting losses. The gains of the amplifiers are selected to offset losses due to the couplings. The overall SNR can be maintained without significant degradation even for large numbers of sensors. In one aspect of the present invention, the amplifiers are located along the distribution and return buses directly after the couplers, except for the last coupler. In a second aspect, the amplifiers are located directly before each coupler. The optical amplifiers preferably are made of short lengths of erbium-doped fiber spliced into the distribution and return buses. Improvements can be made to the SNR when the distribution bus coupling ratios are set at optimal values. The value of the optimal coupling ratio depends upon the amplifier configuration, the excess loss and other configuration parameters. In preferred embodiments, sensors are grouped into parallel configurations in the rungs between the distribution and return buses to increase the number of sensors without a corresponding increase in the number of amplifiers and with an improvement in system performance. The number of sensors per rung is optimized to provide a low noise figure (NF) or a high SNR for each sensor in the array within a reasonable pump power budget.

Optical sensor array having multiple rungs between distribution and return buses and having amplifiers in the buses to equalize return signals

An optical waveguide is formed on a first side of an integrated optics substrate. The optical waveguide is included in a first arm of an interferometer that is arranged to produce an interference pattern. The integrated optics substrate is mounted and arranged such that acceleration of the integrated optics substrate along a selected axis produces a change in the interference pattern. Changes in the interference pattern are monitored and correlated with the acceleration.

Integrated optic accelerometer and method

An acoustic array includes amplifiers and sensor subarrays, both of which are placed along rungs that connect a return distribution bus with both a signal distribution bus and a pump distribution bus. By placing the amplifiers along the rungs, separate buses can be used for distributing the optical signal and the pump energy for the amplifiers, thereby facilitating the use of standardized couplers. Time division multiplexed sensor subarrays are advantageously connected to unique combinations of laser signal sources and signal return buses, in which the laser signal sources generate different optical wavelengths that are multiplexed on the signal return buses. Optical sources include intensity modulators on either side of an amplifier to eliminate extraneous noise between optical pulses. In addition, amplified spontaneous emission (ASE) filters may be advantageously used to reduce optical noise at wavelengths other than those of interest.

Large scale WDM/TDM sensor array employing erbium-doped fiber amplifiers

A system for sensing subterranean acoustic waves emitted from an acoustic source includes a plurality of laser sources, each emitting light at different frequencies; a plurality of subterranean optical sensors, receiving and altering the light in response to acoustic waves; at least one optical detector, receiving the altered light and outputting an electrical signal; and electronics, receiving the electrical signal and converting it into seismic data format. Light from the optical sources is modulated at a plurality of modulation frequencies. The electronics can demodulate the signal by mixing the signal with periodic waveforms having frequencies corresponding to one and two times the modulation frequencies. The modulation frequencies are selected such that at least one of the second harmonic frequencies associated with the modulation frequencies is interleaved in a non-interfering manner within the corresponding set of first harmonic frequencies, and preferably such that at least one of the first harmonic frequencies is interleaved in a non-interfering manner within the corresponding set of modulation frequencies. The hydrophone for sensing the acoustic signals is able to operate at pressures and temperatures of at least 5,000 psi and 130&deg; C., respectively. The hydrophone may be housed in a cable having a diameter less than about 1.5 inches. The hydrophone's sensor preferably includes a reference mandrel, two sensing mandrels, and a telemetry cam, which are aligned in a coaxial, end-to-end configuration to reduce the profile of the hydrophone. The mandrels have hemispherically-shaped endcaps and are joined by flexible interlinks having grooves for receiving optical fiber.

An all-optical polarization splitting switch of the Mach-Zehnder type includes a polarization maintaining fiber, an optical input signal, an optical pump signal, two polarization cross couplers, and a polarization splitting coupler. The polarization maintaining fiber carries the optical signal and the optical pump signal while maintaining polarization orientation. The first polarization cross coupler splits the optical signal into two portions having mutually perpendicular polarization states which have approximately equal power. The optical pump signal, when present, changes the phase of the first portion of the optical signal with respect to the second portion of the optical signal. The second polarization cross coupler combines all the optical power into a combined optical signal. The polarization splitting coupler couples the combined optical signal into a first output port or a second output port in accordance with the polarization state of the combined signal. This configuration eliminates many of the signal phase discrepancies that occur due to thermal instability and unequal fiber lengths which the Mach-Zehnder type switch exhibits. One application for this invention is a polarization splitting switch for a distributed sensor array.

All fiber polarization splitting switch

The length of optical cable affected when splicing in sensors is reduced by cutting and splicing two distribution fiber lines and two return fiber lines to each sensor. The cable includes a spare distribution fiber line and a spare return fiber line. The optical cable is first stripped back to expose the optical fibers therein. For both the distribution and return lines, one fiber is cut at the proximal end of the stripped back portion of the cable, and another fiber is cut at the distal end of the stripped back portion. These fibers are then fused to respective ports on the sensor. Thus, each of the optical channels is formed from more than one optical fiber. The resulting cable is less stiff and more flexible.

System for splicing sensors into a multiple fiber optical cable

Optical sensor array having multiple rungs between distribution and

The present invention significantly improves the signal to noise ratio (SNR) in a passive optical array by adding erbium-doped optical amplifiers between the sensor couplings to offset the coupler splitting losses. Optical amplifiers are inserted between the sensor couplings along the signal path, and the gain of the amplifiers is designed to offset losses due to the previous coupling. The overall SNR can be maintained without significant degradation even for large numbers of sensors. In a first aspect of the present invention, the amplifiers are located along the distribution and return buses directly after the couplers, except possibly for the last sensor. In a second aspect of the present invention, the amplifiers are located directly before the couplers. The optical amplifiers preferably are made of short lengths of erbium-doped fiber spliced into the distribution and return buses. Improvements can be made to the SNR when the distribution bus coupling ratios are set at optimal values. The value of the optimal coupling ratio depends upon the amplifier configuration, the excess loss and other configuration parameters. In alternative embodiments, sensors are grouped into parallel configurations along the distribution and return buses to increase the number of sensors without a corresponding increase in the number of amplifiers and with an improvement in system performance to a certain point.

Growing community of inventors

Thousand Oaks, CA, United States of America

Craig W Hodgson