Using duobinary with first‐ and second‐order optical equalisers for extending transmission distance of optical access networks

Abstract

This study presents the external modulation and direct detection of duobinary signal in optical access networks at 25 and 50 Gb/s with the use of first-order optical equaliser at the transmitter output (pre-equalisation) to compensate the waveform distortion induced by fibre dispersion. The first-order optical equaliser is then replaced by second-order optical equaliser to further improve the bit error rate (BER) performance and extend the maximum transmission distance by compensating the residual dispersion for the first time. The authors explain the enhancement in the BER by analysing the eye diagrams and optical spectra. The authors also investigate non-return-to-zero signal with similar setup parameters for reference.