Integrated TIA-Equalizer for High Speed Optical Link

This paper introduces an integrated TIA (transimpedance amplifier) equalizer combination for a low cost giga-bit optical communication system with perfluorinated graded index plastic optic fiber (GI-POF) offering a large optical bandwidth. To realize the potential cost advantages offered by POF based data link, a large area photodiode is used to reduce costly alignment precision, with a TIA- equalizer. Equalization is needed due to bandwidth limitation resulting from the large photodiode. The photo-detector capacitance with input impedance of the TIA forms a dominant low frequency pole. Equalizer extends the bandwidth of the whole system by introducing a peak in its frequency response at high frequencies to compensate the loss of bandwidth. The main focus is to use an inexpensive, large area photo-detector to increase fiber to detector alignment tolerance simultaneously preserving system speed using the equalizer. This system is for a bit rate varying from 1 to 3 Gbps. The TIA-equalizer combination was implemented with 0.18 mum digital CMOS process using 1.8 V supply.