Pulse response of multimode interference devices

Multimode interference (MMI) devices operating at high data rates are important in optical interconnects and optical networks. Their 1 × N splitting provides a fundamental functionality in these and other applications. To determine the speed limitations of MMI devices, the ultrashort pulse response of these devices is modeled. For example, for 50-fs Gaussian input pulses into a 1 × 16 splitter, the output pulses are severely degraded in coupling efficiency (48%) and completely broken up in time primarily due to intermodal and intramodal (waveguide) dispersion. Material dispersion is found to play only a minor role in the pulse response of MMI devices. However, for 1-ps input pulses into the same 1 × 16 splitter, the output pulses are only moderately degraded in coupling efficiency (86%) and only slightly degraded in shape.