LAUSR

Abstract The Kramers–Kronig (KK) receiver has been used for dispersion compensation in direct detection systems employing external-modulator-based transmitters. In this paper, we investigate the use of the KK receiver for dispersion compensation in a direct detection system based on a directly-modulated laser. We show the validity of the KK receiver by considering a linear contribution to the optical phase arising from a numerical solution of the laser rate equations as a frequency shift of the optical spectrum. The modulated optical signal can then meet the minimum-phase condition required by the KK algorithm. A system model is presented based on the direct modulation of a 10 Gb/s distributed feedback laser with 16-ary quadrature amplitude modulation (16-QAM) subcarrier modulation. The modulated signal is optically filtered, and a 53.5 Gb/s vestigial sideband signal is transmitted over 65 km of standard single-mode fiber. Dispersion compensation is applied after direct detection with a KK receiver. In addition, the impact of the optical filter parameters and receiver sampling rate on system performance are investigated.