Chromatic dispersion compensation employing cascaded parallel optical all-pass filter

This paper presents an alternative method to equalise chromatic dispersion (CD) within a high speed single mode fibre (SMF). The CD is due to the phase delay within the SMF. The CD contributes to the degradation of the quality of the optical pulse propagating in the SMF at high speed which results in pulse spreading. This phenomena will lead to inter-symbol interference (ISI), thus increasing the bit error rate (BER) of the system. In this paper a CD equalisation technique that utilises a cascaded parallel optical all pass filter (Cp-OAPF) is proposed. The Cp-OAPF acts as a phase equaliser which will invert the effect of SMF´s phase delay. The Cp-OAPF is based on a class of digital all-pass filter. Simulation results at BER of 10^-9 showed that the proposed equaliser can increase in the repeater-less length of a point-to-point optical communication system by 7 times with non-return to zero rectangular and Gaussian pulses at 10Gb/s. The signal-to-noise ratio improvement of 19.2 dB and 23.2 dB are achieved for rectangular and Gaussian pulses respectively for error free BER.