Abstract: A class of elements is dependent upon induced absorption for transmitted energy. Absorption is introduced by first pumping an active medium to produce a first excited state--generally an electronically excited state--whereafter the energy level of such excited state is reduced to a lower "metastable" excited state or by pumping directly to such metastable state. Increased absorption for radiation of a quantum energy corresponding with the difference between the metastable and some higher excited state occurs during the time interval that population of the metastable state is maintained. Elements may operate as extremely rapid shutters, switches, modulators, pulse sharpeners, etc.

Abstract: Glass tubes which form an integral part of optical fiber preforms from which optical fibers are drawn are fabricated from tubular structures comprising amorphous powdery particles. The tubular structures are heated so as to fuse the particles thereby yielding a transparent tubular glass structure of optical fiber quality. During the fusing step, the structure is substantially constrained against shrinkage in both the radial and longitudinal direction thereby yielding a glass tube with improved dimensional characteristics.

Abstract: ZnCl.sub.2 optical fibers are advantageously used for transmission of radiation in the infrared portion of the spectrum. Losses as low as 10.sup.-3 dB/km may be obtained when radiation of wavelength between 3.0 and 4.5 microns is transmitted in such fibers. Fabrication techniques allow for the formation of graded fibers to further improve transmission characteristics.

Abstract: An improved reinforced flexible printed wiring board is disclosed. The reinforcement in this printed wiring board is composed of a fabric woven from a yarn of plied continuous filaments of polyester and glass. The fabric is impregnated with an appropriate resin which is subsequently cured. This printed wiring board is found to have improved mechanical and thermal characteristics with little degradation in electrical properties.

Abstract: A device is disclosed which is capable of amplifying optical signals. The absorptive and dispersive properties of a cavity-enclosed nonlinear medium are combined with the transmission properties of the cavity to yield an input-output characteristic curve that displays gain or bistability.