Abstract: A process and apparatus for controlling the feed of an optical fiber or a plurality of optical fibers into a tube while the tube is being formed is disclosed. The process comprises the steps of propelling one or several fibers into a tube with a sufficient force to move the fibers at a speed faster than the speed at which the tube is formed, and of regulating the excess length of fiber by restraining the feed of fiber into the tube at a predetermined ratio with respect to the speed at which the tube is being formed.

Abstract: An optical fiber coupler is described for operatively coupling together two or more optical fibers. Each coupler consists of several biconically tapered fibers. The biconical sections of each fiber are placed side by side or twisted around one another, and fused together. The couplers are typically made of optical fibers having a diameter in the range from about 100 to about 300 microns. The fiber comprises a core of glass having a high index of refraction and cladding of glass with a low index of refraction. The cladding of each biconical section has been reduced by chemical etching, plasma etching, ion-milling, abrasion or the like, to a thickness not exceeding 25 percent of the core diameter, more preferably less than 10 percent and most preferably from about 5 percent to about 10 percent of the core diameter. The couplers are of step or graded index optical fiber. The design can be adapted as multiport access couplers when more than two fibers are involved.

Abstract: A solid state switching device comprises a temperature sensitive resistive element of V.sub.3 O.sub.5 material which exhibits an abrupt decrease in electrical resistance at about 140.degree.C and electrode lead wires attached to spaced points of such temperature sensitive resistive element for connecting the temperature sensitive resistive element to an electrical circuit.