Abstract: A graded base silicon-germanium (SiGe) heterojunction bipolar transistor (HBT)-based electro-optical (EO) modulator includes a graded base HBT and a light beam directed under the graded base HBT and passing through the free carrier plasma within for the purpose of inducing a phase modulation of the light beam.

Abstract: An optical system for frequency-modulation heterodyne detection of an acoustic pressure wave signal. An optical beam is directed into a Bragg cell outside of the fluid medium in which acoustic signals are to be detected. The Bragg cell modulates the incident beam such that two beams of different frequency exit the cell. The two beams are directed into an input optical fiber and the resultant combined beam is transmitted over a desired distance to a fiber optic transducer disposed in the fluid medium. The transducer includes two coiled optical fibers, a reference fiber and a signal fiber, each of which has a different sensitivity to incident acoustic pressure wave signals. The transmitted beam is directed from the input optical fiber through a power divider which splits the beam into two equal parts, one part passing through the reference fiber, the other part passing through the signal fiber. A filter in the signal fiber transmits only a fraction of the light at one of the two frequencies.

Abstract: An optical fiber acoustical sensor for detecting sound waves in a fluid mum. An optical fiber coil through which a light beam is transmitted is placed in a fluid medium. A sound wave propagating through the fluid medium and incident on the optical fiber coil changes the index of refraction of the optical fiber at the area of incidence. The index change causes a phase shift in the transmitted light which is detectable to denote the presence of the sound wave.

Abstract: A multiple-faced optical device comprising a light-responsive element having multiple faces, at least two of the faces constituting input faces for receipt of non-collinear light signals and at least one of the faces other than the input faces constituting an output face from which light signals transmitted through the light-responsive element are emitted. The light-responsive element is further configured to have optically-induced non-linear susceptibility to light signals transversely propagated through the light-responsive element such that at least one portion of the light-responsive element switches between two stable optical states in dependence on the total intensity of the light signals within the light-responsive element. The above-described optical device can be configured to perform various operations, such as AND/OR and INVERT/PASS logic operations, data line branching, signal time delay, and memory storage.