The capacity of arrayed waveguide gratings (AWGs) has increased dramatically, to the point that as many as 400 channels can now be incorporated into a single wafer. A capacity of 1080 channels with 25-GHz channel spacing has been reported in tandem AWGs with a multichip configuration. Although the total capacity of the transport can be increased to the terabit level by use of wavelength-division multiplexing, signal processing in the electrical layer remains a serious problem because of the limits in electrical signal processing speed. The optical signal processing devices that can play an important role in solving this issue include dispersion slope equalizers, polarization-mode dispersion (PMD), equalizers, temporal pulse shapers, and optical label recognition circuits.
by Katsunari Okamoto