Delay distortion compensating circuit for optical transmission system

摘要

A delay distortion compensating circuit for a laser driven optical transmission system comprises a varactor network for producing a time shift of the instantaneous amplitude of the modulation signal applied to the laser that is inverse to the time shift caused by chromatic dispersion of a fiber optic cable used for propagating the output of the laser and laser chirp so that the sum of the two time shifts is substantially equal to a constant. In one embodiment the cathode of the varactor diode is coupled to a center tap of an inductor called a first order delay equalizer, the terminals of which are connected to a source of a modulating signal and the laser. A d-c bias is applied to the varactor by means of a choke. In another embodiment called a low pass structure, a modulating signal is coupled to the laser through an inductor and a parallel combination of a discrete capacitor and a varactor diode is coupled between ground and a node located between the inductor and the laser. D-c bias is provided to the varactor by means of a resistor.