Differential and phase-diverse electrooptic modulators

Abstract

Bandwidth and noise are fundamental considerations in all communication and signal processing systems. The group-velocity dispersion of optical fibers creates nulls in their frequency response, limiting the bandwidth and hence the temporal response of communication and signal processing systems. Intensity noise is often the dominant optical noise source for semiconductor lasers in data communication. In this paper, we propose and demonstrate a new class of electrooptic modulators that is capable of mitigating both of these problems. Fabricated in thin-film lithium niobate, the modulator simultaneously achieves phase diversity and differential operations. The former compensates for the dispersion penalty of the fiber, and the latter overcomes the intensity noise and other common mode fluctuations. Applications of the so-called four-phase electrooptic modulator in time-stretch data acquisition and in optical communication are demonstrated.