Lithium niobate modulators for 10 Gb/s and beyond

As the demand for bandwidth in high capacity fiber optic systems increases, higher speed transmission components are required. Even with the advent of DWDM at 2.5 Gb/s, there is a clear need to increase the line rate of individual channels to 10 Gb/s and 40 Gb/s while concurrently using DWDM. Among the key components required to implement the higher transmission speeds are modulation devices, of which we discuss those made with lithium niobate. 1O Gb/s lithium niobate modulators for Non-Return-to Zero (NRZ) are now being commercially deployed in DWDM systems utilizing both x-cut and z-cut LN crystal orientations. These modulators are of the Mach-Zehnder type with single drive or dual drive configuration, and often contain multi-functionality. One example is the integrated voltage controlled optical attenuator (VOA) on the same monolithic chip as the high speed modulation section. Another example concerns next generation optical transmission systems which utilize RZ based transmission techniques