Study On Modulation Formats And Their Performance In High-speed Optical Transmission System

At present, high-speed optical transmission system is in the direction of single-channel 40Gb/s. With the improvement of channel capacity, optical signals suffer more and more transmission impairments. As one of the key technologies of high-speed long-haul optical transmission system, modulation format could mitigate transmission impairments without great changes in the existing transmission lines. Now on-off keying(OOK) modulation format is not suitable for higher speed system. This paper studies on two main modulation formats:phase modulation and amplitude phase modulation. First, the transceivers of phase modulation and amplitude phase modulation are studied as well as the transmission performances on a WDM system. For phase modulation, the penalty from receiver frequency offset, phase error and delay error is studied. Then, we focus on the influence of self-phase-modulation(SPM) in amplitude phase modulation. Based on the principle of nonlinear phase shift, a pre-compensation method is proposed and the pre-compensation formula is derived.