High Order CAP System Using DML for Short Reach Optical Communications

Carrierless amplitude and phase (CAP) modulation is generating increasing interest for short reach optical communications. In this letter, we present the use of a decision-directed least mean square (DD-LMS) adaptive equalization algorithm for CAP128/256 transmission systems. A novel preconvergence scheme using aided threshold decision is proposed, called decision-assisted modified cascaded multimodulus algorithm. With the help of a DD-LMS-based equalizer, we demonstrate for the first time transmission of 10-Gb/s CAP128/256 signal over 40-km standard single mode fiber using low-cost directly modulated lasers.