Abstract: An optical integrated circuit comprises an optical substrate and an optical waveguide supported by the substrate. A transducer is incorporated into the optical integrated circuit and coupled to the optical substrate. The transducer comprises a region of piezo-electric material and a set of electrodes for applying a voltage to the piezo-electric material for selectively causing the deformation of the piezo-electric material so as to alter the optical path length of the waveguide.

Abstract: An optical fiber tap or coupler in which optical energy is extracted from or coupled into an optical fiber via a bent section of the fiber and in which compression means is provided for applying a compression force along the fiber including along at least the radially outermost portion of the bent section to reduce the likelihood of fracture.

Abstract: A wavelength division multiplexing optical communications system and components thereof capable of using as many as 10.sup.4 channels are described. The system uses a waveguide resonator which is evanescently coupled to an optical fiber or waveguide. There is also an intracavity element optically coupled to the waveguide resonator and the control circuit element which is capable of tuning the frequency of either the intracavity element or the waveguide resonator, or both, to specific frequencies. There may be a plurality of devices optically coupled to each other through the system waveguide to form an optical communications system.

Abstract: A nonintegrating, high sensitivity, wide dynamic range receiver is described. A voltage dependent current source is connected in negative feedback with a forward voltage amplifier. The transconductance of the current source is essentially independent of frequency within the signal bandwidth frequency, and the feedback pole is the dominant pole in the loop gain. To prevent saturation by high intensity input signals the receiver is combined with a range extender circuit.

Abstract: A nonintegrating, high sensitivity, wide dynamic range receiver is described. A voltage dependent current source is connected in negative feedback with a forward voltage amplifier. The transconductance of the current source is essentially independent of frequency within the signal bandwidth frequency, and the feedback pole is the dominant pole in the loop gain. To prevent saturation by high intensity input signals the receiver is combined with a range extender circuit.

Abstract: A multistage avalanche photodetector in which the ionization energy is provided by an energy band discontinuity is described. The photodetector provides low noise optical detection at low voltage.