Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.