160 Gb/s optical time-division demultiplexing using concatenated electroabsorption modulators

Optical time-division multiplexing (OTDM) is a technique that allows optical communications at bit rates higher than those possible with electronic time-division multiplexing (ETDM). Performing the high-speed multiplexing and demultiplexing operations in the optical domain avoids the bandwidth limitations of electronics. Electroabsorption modulators (EAM) are commonly used for OTDM demultiplexing due to their high extinction ratios and ease of implementation compared to all-optical demultiplexers. The static and dynamic optical absorption characteristics of two EAMs are evaluated. An optical sampling oscilloscope (OSO) with 700 GHz bandwidth allowed the accurate measurement of dynamic absorption properties. Absorption is shown to vary with modulation voltage and frequency. The optical gating window is characterized and compared to simulated gating windows; showing that simulation based on dynamic absorption characteristics produces a more accurate result. Optical demultiplexing at 160 Gb/s and lower bit rates is demonstrated, and the importance of gating window optimization is illustrated.