Bringing telecom networks up to speed [planar lightwave circuits]

Planar lightwave circuits (PLCs) provide various important devices for WDM systems, TDM systems, and subscriber networks. This article reviews the recent progress and future prospects of PLC technologies including arrayed-waveguide grating (AWG) wavelength filters, optical add/drop multiplexers (ADMs), programmable dispersion equalizers, and hybrid optoelectronics integration technologies. Continuous improvements in waveguide fabrication, circuit design, and device packaging will further bring these technologies to a higher level of integration of optics and electronics, aiming at the next generation of telecommunication systems.