Novel electro-optical pre-distortion technique and its application in externally modulated CATV transmission systems

Abstract

Conventional linearization techniques such as electrical pre-distortion or optical feedforward methods have been applied to Mach-Zehnder interferometer (MZI) modulators for CATV transmission systems. However, both methods can only ensure that the output of the MZI modulator meet the standard CATV requirements on composite second-order (CSO) and composite triple beat (CTB), but cannot guarantee a satisfactory end-to-end system linearity. In this paper, we propose and demonstrate a novel linearization technique, which can simultaneously suppress the nonlinear distortions (NLDs) generated in a transmission system and increase the received carrier-to-noise ratio (CNR). This technique is based on offsetting the MZI bias voltage from its inflection point. Both analytical and experimental results are presented.