Leland Stanford Junior University

Bell Telephone Laboratories

Cassius C Cutler

Herbert J Shaw

Robert C Youngquist

Steven A Newton

Wayne V Sorin

Kenneth A Fesler

John Ormond Limb

Janet L Brooks

Ross A Lemons

Walter L Bond

A fiber optic saturable absorber for processing optical signals comprises an optical fiber from which a portion of the cladding is removed to form a facing surface. A light-absorbing substance having non-linear light-absorbing characteristics is applied to the facing surface such that a portion of the optical signal energy is transferred from the fiber to the substance where it is absorbed. The device selectively attenuates the optical signal and noise, and can be used to reduce pulse waveform distortion caused by pulse broadening and by amplification of system noise.

Single-mode fiber optic saturable absorber

A distributed sensor system including an optical source having a short coherence length for optionally continuously monitoring each sensor in the system. In one preferred embodiment, an array of fiber-optic sensors are organized in a ladder configuration, with the sensors positioned in spaced relation and defining the rungs of the ladder. Light transmitted through the sensors is multiplexed onto a return arm of the ladder, with sensor spacing being such that interference between light from different sensors is prevented. The multiplexed signals are received by an optical fiber receiver which couples the multiplexed light with an interfering optical reference signal to produce a phase difference signal representing conditions influencing selected sensors. Embodiments are disclosed for use of either pulsed or continuous wave light sources. In another preferred embodiment, the sensors comprise a plurality of Mach-Zehnder interferometers connected in series configuration by a common optical fiber, which provides multiplexed output signals from the sensors to a plurality of Mach-Zehnder interferometers comprising receivers. The optical path length differences between the arms of each of the sensors are selected to prevent interference between the multiplexed sensor output signals from various sensors. The optical path lengths through the sensors and receivers are structured so that each receiver produces a phase difference signal relating to conditions affecting light transmission through a specific sensor. A phase and amplitude modulation technique is disclosed for providing heterodyned output signals from the distributed sensor system.

Coherent distributed sensor and method using short coherence length

Method and apparatus for improving the sensitivity of Sagnac gyroscopes and other interferometers utilizing a fiber optic loop by minimizing the effects of backscattered radiation. In one disclosed embodiment, the amplitude of coincident backscattered radiation is significantly reduced by applying the light in the form of a pulse of short duration and gating the output so that only the scattered energy from a short length of the fiber contributes to the interfering wave. The interference is reduced even further by processing or constructing the loop to eliminate the scattering sources in the short segment which can give rise to coincident backscattered power.

Fiber optic loop interferometer and method with coincident backscatter

A fiber optic tapped delay line is disclosed in which a number of bends in a single optical fiber are formed to obtain taps of an optical signal traveling in that fiber at each bend location. Light removed at the bends is directed to a focusing lens, which focuses the light onto a photodetector acting as a summing device to produce a frequency-filtered output of the light signal traveling in the fiber. The device's response as a transversal filter is enhanced by weighting the taps either by use of a cylindrical lens, or by selectively masking a portion of light emitted by selected individual taps.

Microbend optical fiber tapped delay line

An acoustic microscope for scanning an object stereo-optically and with both dark field and light field imaging. The microscope focuses acoustic waves on a focal point and moves the object in a planar raster pattern through the focal point. The acoustic waves are modulated by the object and displayed on an oscilloscope. The microscope permits the rotation of the object about the focal point so that two, azimuthally displaced images of the object can be obtained. These two images can be observed as one three-dimensional image in a lenticular stereoscope. In addition, the microscope can scan the acoustic waves scattered by the object and display a dark field image of the object.

Acoustic microscope for scanning an object stereo-optically and with

Apparatus is disclosed for selecting video frames indicative of still pictures from successive video frames, a portion of which are indicative of moving objects and the remaining frames are indicative of still objects. The input and output video signal paths of a frame memory are completed through switches. A speed measurement circuit utilizes the signals at the input and output of the frame memory as the video signal is applied thereto to identify frames indicative of still objects. A logic circuit that operates the switches responds to the output of the speed measurement circuit by changing the position of the switches to retain the content of the frame memory and apply same to the output signal path. Timing circuits are also advantageously utilized to slow down the selection rate of frames indicative of still objects and force the selection of a more recent video frame when the speed of movement fails to fall below a predetermined value.

Growing community of inventors

Palo Alto, CA, United States of America

Cassius C Cutler