Dispersion compensation techniques using planar lightwave circuits

The channel number and bit rate per wavelength is being increased in wavele ngth division multiplexing (WDM) communication systems. Techniques to compe nsate precisely for chromatic and polarization-mode dispersion in a fiber a re becoming increasingly important for such advanced high bit rate WDM syst ems. In this article, we report on dispersion equalizers fabricated on plan ar lightwave circuits (PLCs). First, we describe a chromatic dispersion equ alizer focusing mainly on a WDM dispersion slope equalizer that consists of a lattice-form dispersion equalizer array and an arrayed-waveguide grating (AWG). Then we describe the basic operation of a polarization mode dispers ion equalizer, in which a polarization controller and a delay line are inte grated on one substrate.