Abstract: A predistortion circuit for cancelling third-order distortion products produced by a non-linear device includes a signal source which drives a first and second circuit branch each including a plurality of series connected diodes having approximately exponential transfer functions. The output signal taken as the summation of the two signals processed by the branch circuits is coupled through an amplifier to the device to be linearized. In an alternate predistortion configuration, the signal source drives a phase splitting means which produces two signals of equal amplitude but opposite phase, wherein each of the signals drives a respective one of the branch circuits. A phase combining means performs an out of-phase combination of the signals processed by the branch circuits.

Abstract: A second-order predistortion circuit for linearizing a nonlinear device having a transfer function of the form F=C.sub.1 I.sub.1 -C.sub.2 (I.sub.1).sup.2, where I.sub.1 is a current applied to an input of the nonlinear device, and C.sub.1 and C.sub.2 are constants. The nonlinear device is typically a laser diode. The predistortion circuit includes a field effect transistor biased for square law operation. An input voltage is applied between the gate and source electrodes of the field effect transistor. An amplifier is connected between the drain electrode of the field effect transistor and the input of the nonlinear device. The gain of the amplifier is selected to minimize second-order distortion in the output of the nonlinear device as a function of the input voltage to the field effect transistor.

Abstract: An optical transmission system includes a power splitter for dividing an RF input signal into a plurality of intermediate signals each assigned to a respective one of a plurality of parallel optic links. Each link optically transmits its respective intermediate RF signal over a respective fiber line before being detected at a receiver end. The detected signals are combined by an RF power combiner into an output signal having an enhanced signal to noise ratio that is better by 10 log n dB over that of a single link, where n is the number of parallel links. In order to permit operation at arbitrarily high frequencies, a pilot tone delay equalization circuit is coupled to each link at the receiver end for equalizing the delay variations between the various fiber paths.

Abstract: A high speed photodetector, for use with semi-conductor lasers or the like, is configured to receive light signals upon a beveled detector facet, directing the incident light through a semiconductor window layer to the detector's junction region.

Abstract: A transient suppression circuit is provided for starting up or turning off a light emitting diode, such as a diode laser. The circuit minimizes the possibility of turn-on or turn-off transients or overshoot, employing a time delayed voltage. A diode circuit is used which generates an output voltage equal to the higher of two voltages at its two inputs, one input being the time delayed voltage and the second being derived from photodetector which detects electromagnetic radiation emitted by the light emitting diode. The circuit also utilizes a three terminal voltage regulator which maintains a constant voltage between its sense terminal (output from the diode circuit) and its output terminal.