Adaptive Blind CSO Cancellation Technique for RoF Systems Implemented by Using DMLs

We report on the adaptive cancellation technique of the dispersion-induced composite second-order (CSO) distortions for use in radio-over-fiber (RoF) systems implemented by using directly modulated lasers (DMLs). The proposed technique utilizes the magnitude of the CSO distortions measured at outside the signal’s bandwidth as a cost function of the steepest descent algorithm. As a result, this technique can blindly cancel out the CSO distortions without the necessity of measuring any device and fiber parameters used in the RoF system. The effectiveness of the proposed technique is confirmed in the RoF link implemented by using a 1.55- $\mu \text{m}$ DML and is capable of transporting 24 100-MHz filtered-orthogonal-frequency-division-multiplexing signals in 64 quadrature amplitude modulation format.