40Gb/s electro-absorption modulated NRZ and RZ sources

Electro-absorption modulated sources are likely to be key components in the evolution of optical communication line rates from 10Gb/s to 40Gb/s. Compared with the LiNbO₃ alternative EA modulators are more compact, less expensive, compatible with monolithic integration, and offer lower drive voltages. However, fabrication complexity and open questions concerning the fidelity with which they transmit information make the exact role of 40Gb/s EA modulators in advanced communication systems somewhat unclear. In this talk we will describe the design, fabrication, and transmission performance of 40Gb/s EA modulators configured for both NRZ and RZ operation. For NRZ transmission the device structure consists of a short MQW modulator with spot-size converters on the input and output ends. Tandem EA modulators for pulse carver and data encoder functions were monolithically integrated along with a semiconductor optical amplifier (SOA) and input/output spot-size converters to explore RZ transmission. Both single and tandem modulator designs are realized using semi-insulating InP current confined buried heterostructure technology. Modulation bandwidth of better than 50 GHz is demonstrated along with a fiber-to-fiber insertion loss of less than 6dB for the single modulator design. The carver/encoder configuration with onboard SOA yields better than 0dB insertion loss. Transmission impairments were studies using both designs.