Abstract: The present invention relates to an optical logical AND gate comprising an erbium doped waveguide which is attenuating at a signal wavelength and responsive to pump light energy to be transmissive at a signal wavelength. A first laser pump excites a portion of the waveguide. A second laser pump excites a remaining portion of the waveguide. The waveguide is only transparent to transmit a signal if both the first and second pumps excite the waveguide together. The optical AND gate of the present invention can be used as the control element of an N.times.N matrix. A number of first ports and a number of second ports are interconnected by erbium waveguide AND gates. Pump light is switched to a selected first port. Pump light from a second pump is switched to a selected second port. Only the erbium waveguide gate interconnecting the selected first and second port is transmissive to switch a signal. All other gates are attenuating and other signals are accordingly blocked.

Abstract: This invention relates to a method and apparatus for switching an optical signal from one or more input ports to one of a plurality of output ports. A beam is launched into the input port. By controllably switching a switching element, such a liquid/air switch selection can be made selecting a plurality of deflections along a first plane to direct a beam along the first plane to one of a plurality of output locations; the beam is received from one of the plurality of locations and is directed along a second plane intersecting the first plane, to direct the beam to one of the output ports. In a preferred embodiment, the switch includes two prisms each having switching elements at end faces of the prisms.

Abstract: A system of interconnected functionally identical modules for switching P optical signals to P locations in a non-blocking manner is disclosed. Each of the functionally identical modules provides a same function, which may or may not be provided in an identical manner. Each module has several of first ports and several second ports optically coupled to second ports of other modules. Switching means are provided for switching means for switching between the first ports and the second ports. Each module has at least a second port is directly coupled to another second port. Providing a system wherein modules are identical provides numerous advantages. The architecture further provides the advantage of ease of repair within no disturbance to communications being handled by other modules.

Abstract: An apparatus and electronic circuit for the measurement of fluid levels in containers. The circuit and apparatus constitute an instrument which measures fluid levels by optical means. Only light signals are used near the fluid itself. The instrument thus provides an intrinsically safe method of measuring fluid levels in the presence of explosive or flammable fluids, vapours or gasses, or in containers which must be electrically isolated.

Abstract: A fibre sensor used for the measurement of ambient refractive index has a tapered end. The taper of the optical fibre generates cladding modes which undergo multiple reflections at the external surface of the fibre, and therefore gives high sensitivity to the ambient index. A tapered fibre is also relatively immune to contamination by adhering droplets when the end reflection is used since the droplets tend to move to the point of greatest radius, which tends to be away from the point where the Fresnel reflection of interest occurs. The reflection from the tapered end of a multimode fibre is measured as a function of ambient refractive index. In contrast to a square-cleaved fibre, the reflection from a tapered fibre is monotonically related to the ambient index, removing an ambiguity that occurs when refractive index is measured by Fresnel reflection at normal incidence. Tapered optical fibres are suitable for probes to identify the interface between immiscible liquids.

Abstract: Optoelectronic switching matrix which switches multiplexed input signals to narrowband output lines. Each crosspoint of the matrix is comprised of a heterodyning photosensor, which optically receives the multiplexed input signal and electrically receives a selectable local oscillator signal. The difference frequency can thus be selected to be within the passband of a low pass filter whereby narrowband output signals can be received from the input signals without requiring the use of a demultiplexer.

Abstract: Photoconductors with channels that lie in the surface depleted region of a GaAs structure are described. These devices have nanoampere bias current, and exhibit photoconductive gain. In contrast to other photoconductors, their low frequency responsivity is of the same order as that in the GHz region, alleviating problems of equalization necessary in receiver applications. As well, these devices exhibit over 60 dB isolation as optoelectronic switches.

Abstract: An optoelectronic assembly for converting a signal between optical and electrical form, or vice versa, consists of a dielectric substrate and a semiconductor substrate. These substrates are fabricated separately and then brought together with major faces in intimate contact with each other. The dielectric substrate has a pair of metallic electrodes on its surface and a waveguide extending to a coupling region. The semiconductor substrate has an active optoelectronic device, e.g. a photodetector or light emitting device, whose optically active portion is brought into optically coupling relationship with the coupling region of the waveguide. At the same time electrically contacting regions of the optoelectronic device are placed in electrical contact with respective ones of the pair of metallic electrodes on the dielectric substrate.

Abstract: This invention utilizes an opto-electronic matrix switch to select a set of fixed value phase shifters. Signals which are selectively phase shifted by this apparatus may be introduced into the signal path of each antenna element of a phased array antenna. In one embodiment the input signal is converted into an intensity modulated optical signal which is then split between paths of different length to provide different delays and hence different phase shifts. The matrix then selects a particular set of the phase shifted signals which are converted back to electrical signals and fed to the antenna array elements.

Abstract: An optical coupler for a fiber optic communication system, which couples one band of wavelengths out of the fiber while allowing others to be carried further. This allows wavelength division multiplexing of different signals within a single fiber. The preferred embodiment of the invention is comprised of a waveguide having aperiodic corrugations in one wall and a Fabry-Perot type resonator enclosing the waveguide around the corrugations with its axis transverse thereto.