40 Gb/s CAP32 System With DD-LMS Equalizer for Short Reach Optical Transmissions

Carrierless amplitude and phase (CAP) modulation is a promising candidate for short reach optical communications. In this letter, we propose the use of decision-directed least mean square (DD-LMS) adaptive equalization algorithm for high-order CAP transmission systems. The optimal length of taps and step size of DD-LMS algorithm is investigated for 30 Gb/s and 40 Gb/s CAP32 systems. A hybrid equalization technique that consists of DD-LMS and its aided two-stage pre-convergence is proposed that allows experimental transmission of 40 Gb/s CAP32 40 km standard single mode fiber (SSMF).