Abstract: The present invention is directed to a process and product of a process in the field of optical directional coupler switches. The application of laser light to the input ports of a coupler switch at a power level approximately twice or greater the operational power level that has been discovered to cause optical damage produces a remedial effect of stabilizing the switching characteristics of the optical coupler switch. The resulting optical coupler switch has improved transmission characteristics when measured by a transfer function over that of an untreated coupler switch.

Abstract: An improved photodector which in utilizing a low noise load network instead of a resistor has the advantages in signal-to-noise ratio of a large load resistance without the deleterious effect on response time. The circuit includes a conventional photodiode with an operational amplifier at its output. The load network is disposed in the feedback path of the operational amplifier. It consists of a second operational amplifier, a fixed resistor and a variable resistor.

Abstract: A circuit is disclosed for impedance matching an electrical signal-generating transducer to an electrical signal-processing amplifier while substantially retaining both the original signal-to-noise power ratio and the original signal amplitude at the input to the amplifier. A load resistance of a value substantially equal to twice the characteristic resistance of the transducer is coupled across the amplifier input, while a negative low-noise resistance approximately equal in magnitude to the source resistance is coupled in series with the load resistance. A transmission line having a characteristic impedance approximately equal to the transducer resistance is coupled between the transducer output and the series-coupled load resistance and negative resistance.

Abstract: A class of two-terminal active networks which simulate low-noise-temperature resistors is disclosed. A single differential-input operational amplifier connected with a feedback resistor in an inverting amplifier configuration comprises the active element of the network. A resistive voltage divider feedback arrangement comprises the remainder of the circuit. Either positive or negative simulated resistors can be obtained with a wide range of equivalent resistance values and effective noise temperatures.

Abstract: A class of two-terminal active networks which simulate low-noise temperature resistors is disclosed. A single differential-input operational amplifier connected with a feedback resistor in an inverting amplifier configuration comprises the active element of the network. A dual-transformer feedback arrangement or a single transformer feedback arrangement comprises the remainder of the circuit. Either positive or negative simulated resistors can be obtained with a wide range of equivalent resistance values and effective noise temperatures.