Abstract: A fibre optic gyroscope arrangement having a nulling feedback control loop, the gyroscope including means 40 for varying wavelength of the light source 41 for a predetermined period of time at switch-on of the gyroscope and means for subsequently operating the light source 41 at a fixed wavelength.

Abstract: Connection into and out of digital integrated circuits is made optically, the input being implemented by floodlighting appropriately placed photodiodes at the input points and the output by on chip commutative switching of the connect centers onto a common output pad which drives a light emitting source. Communicating chips are synchronously clocked at the commutation rate to achieve required interconnect configuration via time division multiplexing.

Abstract: In a coherent optical transmission system an input optical signal is amplified by being frequency down converted to an intermediate frequency, for example by means of a photodiode (1) and a reference optical local oscillator signal, and the photodiode output current is amplified in a GaAs FET wideband amplifier (6) and inserted on an optical carrier signal comprised by the reference signal by means, for example, of an integrated optical single sideband modulator (up converter) (7). By use of the same optical local oscillator to drive both the photodiode down converter and the integrated optic single sideband up converter, input/output coherence is ensured. The optical local oscillator may be comprised by a GaAlAs laser (3) stabilized to an "atomic" standard (4,5). Channel dropping/insertion may be carried out at the intermediate frequency, for example following the amplifier (6).

Abstract: In an optically controlled phased array radar control information in the form of microwave frequency modulation of an optical carrier is transmitted by optical waveguide from a central processor to each of the antenna elements. Phase shifts introduced by each of the individual waveguides are then monitored to provide a compensation signal used either to regulate the phase shift or to offset the phase of the modulation applied to the waveguide at the central processor end.

Abstract: An acousto-optic isolator for a semiconductor laser diode comprises a Fabry-Perot resonator tuned to the laser optical frequency f.sub.o followed by an acousto-optic Bragg diffraction device utilizing surface acoustic waves of frequency f.sub.a launched from a transducer. Light focussed by a lens to the load has a resultant frequency f.sub.o +f.sub.a. Any light reflected from the load suffers a further change in frequency to f.sub.o +2f.sub.a in the diffraction device and hence is blocked by the resonator. Undiffracted light can be detected at a photo-detector and used in a feedback control loop to stabilize the light source to the resonator.

Abstract: A two-dimensional acousto-optic deflection arrangement including a source (10a) of electromagnetic radiation, means (18) for modulating the source, means for collimating the output of the source into a beam, and an acousto-optic deflection means (12a) situated in the path of said beam, the deflection means comprising a rectangular body of acousto-optic material provided on two adjacent surfaces with electro-acoustic transducers arranged to launch orthogonal bulk acoustic waves into the material transverse the direction of propagation of radiation through the material whereby the focussed radiation can be scanned in two dimensions over an area illuminated by a source (20) secondary illumination. Typically the scanned area comprises a thermo-optically addressable liquid crystal display device (17).

Abstract: A solid state electro-optic switch employing first order electro-optic effect in bulk material. Selectively energized contact patterns define divergent optical waveguide paths in the bulk material.