A sensitive towed optical fiber sensor array 50, wherein the fiber sensors (60A-60N) are connected in parallel, and the optical fiber cable (34) is paid out from the towing ship at a velocity about equal to but opposite to the velocity of the towing ship. The fiber sensors (60A-60N) are immune to electromagnetic interference, and the output of the sensors can be isolated readily to the parallel hookup of the sensors. Turbulence and acceleration noise is greatly reduced due to the manner in which the fiber cable (34) is paid out, and crosstalk between sensors is eliminated.

Reduced noise fiber optic towed array and method of using same

A fiber optic sensor array has multiple segments, each capable of detecting a physical condition such as an acoustic wave. The segments are separated by weak reflectors such as fiber optic Bragg gratings. Light from a light source is input into the input end of the array. Light reflected by each of the reflectors has a phase shift representing the effects of the physical condition on all of the segments from the input end to that reflector. To address a specific reflector, the return light is demultiplexed. This demultiplexing is done by modulating the light input into the input end of the array with a pseudo-random bit sequence and correlating the output with a time-shifted version of the pseudo-random bit sequence to isolate the part of the output caused by that reflector. To address a specific segment, the phase shifts from two adjacent reflectors are determined. The return light can be strengthened by mixing it with a portion of the light picked off from the light source.

Coherent reflectometric fiber Bragg grating sensor array

An on-chip data communications infrastructure includes a hybrid, photonic/electronic network. The network includes a plurality of interconnected optical switches, each under the control of an electronic router. The electronic routers are connected in a fashion similar to the optical switches, forming a parallel, photonic/electronic network. Electronic path setup messages are routed through the electronic network. At each hop, a photonic switching element in a parallel, photonic network is reserved. When the electronic path setup message reaches its destination, a chain of reserved optical switches is ready to channel the optical data through the photonic network.

Systems And Methods For On-Chip Data Communication

An optical fiber sensing system for detecting intrusion of optical fiber or optical fiber cables includes an interferometric arrangement. Two ports (28, 30) of a four port splitter (25) are connected to a source (26) of optical power such as a laser, for example, and to a detector (32). The other two ports (46, 48) are connected to ends of a length (50) of monitoring optical fiber. An input signal to the splitter is split with one subsignal being directed in one direction around the length of optical fiber which serves as a common path between the two ports. The other signal is caused to travel around the common path in an opposite direction. The split signals are recombined in the splitter and their phase difference measured as a detectable pattern by the detector. Should there be intrusion of the optical fiber or a cable containing the monitoring optical fiber, the pattern which is detected will change a significant amount.

Methods of and systems for optical fiber sensing

An optical fiber extends down hole from an OFDR. A first set of sensors with a centrally-located reference reflector is disposed over a first fiber length, and a second set of sensors with a centrally-located reference reflector is disposed over a second fiber length. The sensors of the first and second sensing lengths are positioned at slightly offset positions from the reference reflectors so as to interleave the reflected signals. Additional sensing lengths may be similarly interleaved. The system is used by sending an optical signal along the optical fiber, detecting a reflected optical signal, separating the optical signal into component signals, and extrapolating a well condition therefrom. Another method includes creating a low frequency signal component in a reflected optical signal by placing at least one sensor beyond a Nyquist sampling distance limit, detecting the low frequency signal component, and extrapolating a well condition therefrom.

System and method for monitoring a well

A fiber optic sensor array (10) comprises a single transmit optical fiber (14) for guiding an incident optical signal through a plurality of sensing segments (20A, 20B, 20C) in the transmit optical fiber (14) arranged in a series array. The sensor array (10) may include a single return optical fiber (16), or the sensors may be arranged in groups (20A, 202B, 202C) with all the member of one group (202A) being connected to a corresponding return fiber (212). Optical couplers (18A, 18B, 18C) formed between the transmit (14) and return optical fibers (16) couple a portion of the incident signal into the return fiber (16) after the signal propagates through each sensing segment (20A, 20B, 20C). A loop (100A, 100B, 100C) is formed in the transmit fiber at each optical coupler (18A, 18B, 18C) so that the incident signal travels through the sensing segments in one direction and through the return fiber in the opposite direction. The couplers may be identical and may be have either symmetrical or asymmetrical coupling coefficients. Asymmetrical couplers (290, 308, 310) may be used to attenuate the intensities of undesired signals that recirculate in the loops of the array.

Michael R. Layton

Papers

Fiber optic sensor array and method