Absb'nct-Penalty free wavelength conversion is demonstrated at 2.5 GbiVs over a wavelength span of 12 nm by the use of SOA's in a Mach-Zehnder configuration. An increase in the extinction ratio is measured for the converted signal compared to the input signal implying signal regeneration as well as wavelength conversion.

Measurements of low-impedance thin-film tunneling junctions at room temperature frequently yield inaccurate values for the tunneling resistance. In some cases the indicated resistance is negative. A theory is developed which shows that the finite resistance of the metal films can account for the observations. Results, given for the resistance of a tunneling junction as a function of temperature, show good agreement between theory and experiment.

Investigation of the characteristics of Josephson tunneling in tin-t~n-oxide--tin junc~ions .showed ~at pulse voltages with sharp risetimes were being generated. Pulse amphtude across the Junction r~mamed constant and equal to the energy gap voltage V., but pulse frequency could be changed.ove~ a 25.1 ra?ge by a change in bias voltage from 0 to an upper limit approx~atelr equal to V./2. The osclll~tIon ~echarusm is that of switching between the pair-current state of the Junction at V = 0 and. the quasIparticle-current t t t V -V The external circuit maintains the switching cycle and determmes the output frequency sa e a -. . . . h db' d leV) characteristics. Using the L/ R time constant of .the .external clrc~lt and t e assume aSlc c cu~e f the junction in the absence of relaxation osclllatlOns, calculatlOns were made that acc~rately descnbe ~he observed dc leV) curves, frequency, and waveforms, including their dependence on biaS voltage and magnetic field.

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