Ortel Corporation

Howard L Loboda

Henry A Blauvelt

Israel Ury

David B Huff

John S Frame

Henery A Blauvelt

This optical receiver is capable of receiving broadband R-F modulated signals transmitted over fiber-optic cable. The receiver comprises a photodiode impedance matched to the input of an low noise, low distortion amplifier by an impedance matching transformer. A passive tuning network is placed between the photodiode and the transformer to improve the high frequency performance of the receiver. Distortion of the optical receiver is further reduced by cancelling even power distortion products from out of phase signals generated by the photodiode.

Broadband optical receiver with passiner tuning network

An electronic circuit provides a linear output from an amplitude modulated transmission device such as a semiconductor laser which has inherent distortion. The distortion of the nonlinear device is compensated by applying a predistorted signal equal in magnitude and opposite in sign to the distortion introduced by the nonlinear device. The input signal is split into two or three paths with primary part of the signal applied directly to the device, with a time delay to compensate for delays in two secondary paths. One secondary path generates even order intermodulation products and the other generates odd order intermodulation products. These are recombined with the primary signal in proper phase and amplitude for cancelling distortion in the output device. A distortion generator in each secondary path generates adjustable amplitude intermodulation signals. A tilt adjustment is made to compensate the amplitude of the predistortion for frequency dependence of the amplitude of the distortion. Phase of the distortion signal is adjusted to be in proper phase relation with the distortion of the device. In the even order path there are means for adjusting predistortion at an intermediate frequency so that the distortion is cancelled near the upper, lower and intermediate portions of the frequency range of the device.

Predistorter for linearization of electronic and optical signals

An electronic circuit provides a linear output from an amplitude modulated transmission device such as a solid state laser which has inherent distortion. The distortion of the nonlinear device is compensated by applying a predistorted signal equal in magnitude and opposite in sign to the distortion introduced by the nonlinear device. The input signal is split into two paths with primary part of the signal applied directly to the device, with a time delay to compensate for delays in the secondary path. A predistorter in the secondary path generates harmonic signals, the amplitude of which is adjusted to match the amplitude of the distortion. A tilt adjustment is made to compensate the amplitude of the predistortion for frequency dependence of distortion. A fine adjust of the delay is also included so that phase of the predistortion signal is in proper phase relation with the primary signal. A push-push amplifier is used as a distorter, with bias current unbalanced to produce net odd harmonics as well as even harmonics of the fundamental frequencies.

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Los Angeles, CA, United States of America

Howard L Loboda