Predistortion circuit design for II and III order simultaneous linearization in multiservice telecommunications apparatuses

We have developed a completely analog, low-cost, multioctave predistortion circuit to compensate second- and third-order distortions in Radio-over-Fiber laser-based telecommunications equipment. The predistorter has been designed on the basis of both a circuit model of commercial DFB lasers and a complete compensation procedure previously developed. A first prototype has been realized and fully tested in the frequency range 500 MHz - 2 GHz, used with GSM, DCS and GPRS cellular services. Some modifications to the relevant architecture have led to a second final predistorter prototype able to reduce of about 9 to 15 dB both the laser second- and third-order harmonic distortion components falling within the DCS band (1710-1880 MHz).