Northern Telecom Limited

Other

Jozef Straus

William J Sinclair

Tibor F Kovats

Gary S Duck

Robert I MacDonald

Anthony J Springthorpe

John C Dyment

Masamichi Yataki

Otto Istvan Szentesi

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. A single signal can be switched to a selected output or to a number of outputs to achieve a broadcast function. Advantageously, active switch elements are removed from the signal path, and the signal is switched passively. This switch unit is used to advantage in a multiple stage switch architecture.

Optical switching gate

Opposed ends of optical fibers are fused within a holding member, by heating the fiber ends by means positioned in, or on, the member. A self-contained package can be provided to which an electric current is applied, or some other heating method.

Fused optical fiber splice element

A passive fiber optic device and optical fiber connected to it are packaged in a solid block of a bismuth containing fusible alloy. The alloy exhibits appreciable expansion on solidification, negligible dimensional change after solidification, and a low thermal expansion coefficient. Coupled with its low melting point and glass wetting ability, the alloy is uniquely adapted for forming a hermetic seal with glass. By molding as a solid block, the packaging operation is rendered simple and rapid.

Hermetic optical attenuator

An optical switch having a light input side and a light output side where there are a plurality of optical waveguides with light collimating lenses on one of the sides with the lenses in spaced positions and, on the other side there is an optical waveguide with a light collimating lens. To enable light to be transferred between the latter waveguide and any of the other lenses, it is movable to bring its lens into any of a plurality of switch positions, each corresponding to the position of one of the other lenses, and means is provided to move the lens selectively between positions. In preferred arrangements, the plurality of lenses are arranged around at least one pitch circle but a linear arrangement of lenses is also possible. An electric stepping motor is ideally used for the switching operation.

Optical switch

An electro-optic device for stabilizing the output level of a Burrus-type light emitting diode (LED) utilizes a photodiode to monitor side emission from an active region of the LED. Side emission closely tracks top emission, which is launched into an output fiber. An electrical analog is derived from the monitored side emission and is applied in a feedback loop to control modulation level or bias current to the LED. In this way, peak optical output (for digital systems) or r.m.s. output and linearity (for analog systems) is stabilized. The monitoring photodiode and the LED may be spatially separate or may form a unitary structure.

Electro-optic devices

An optical transmitter suitable for analog transmission in optic fiber communication systems utilizes two matched light emitting diodes to achieve distortion reduction.

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Ottawa, Canada

Jozef Straus