Abstract: A graded index, multimode optical waveguide. The waveguide is characterized by a graded profile region, followed by an abrupt drop in index, then a region of constant index. At predetermined intervals, the fiber is modified to have a conventional graded index profile to suppress unwanted modes propagating along the guide.

Abstract: A repeatered submarine cable has a composite inner conductor for accommodating a system of optical fibers therein. The cable strength members include a central elongated filament and plural layers of stranded steel wires separated from the central filament by an annular insulating core member, in which the optical fibers are embedded. A metallic tubular jacket surrounds the stranded steel layers to provide both a DC path for powering the optical repeaters and a hermetic moisture barrier for the fibers.

Abstract: A plurality of crossed input and output optical channels are arranged in coordinate fashion to define a crosspoint array. A pair of jointly operable mode switches are disposed in the respective channels that form each crosspoint. Operation of the mode switch on the input side of a selected crosspoint causes incident light energy to be converted from a first mode (e.g., the TE.sub.0 mode) to a second mode (e.g., the TM.sub.0 mode). When the so-converted mode reaches the crosspoint, a reflection-type filter transparent to the first mode reflects such second mode into the other channel, where it is then reconverted back to the first mode by the operated mode switch on the output side of the crosspoint. The overall assembly may be formed by thin-film techniques on a supporting substrate.

Abstract: A multiplex radio transmission system is provided with facilities for initiating protective switching from a working channel to an idle channel of the system when the signal to interference ratio on the working channel falls below a predetermined threshold value. A precise square-law detector derives, from the separate information and interference components of a signal on the working channel, a DC component and a difference-beat AC component which are processed to yield a quantity indicative of the desired signal to interference ratio. When such ratio falls below the predetermined threshold value, switching to an idle channel occurs in a manner similar to conventional signal-to-noise dependent protective switching arrangements.

Abstract: A high-strength, electrically matched and constructionally simple anchor assembly is provided within a cable-repeater coupling for securing the front end of a submarine cable inner conductor within the coupling. The anchor member of the assembly includes a pair of centrally apertured, axially abutting discs formed from reinforced glass fibers, together with a metallic disc-like nut that abuts the front surface of the front-most disc. The stranded cable inner conductor terminates short of the discs, and is crimped within the rear end of a tube that extends through central apertures of the discs and which is affixed to the nut at its front end. The composite nut-disc member is embedded in a load-bearing cylindrical polyethylene body that is in turn captured within the anchor housing of the coupling.