The object of the present invention is to provide a compact dispersion slope
equalizer by which it is possible to simultaneously recover distorted waveforms
of WDM signals by dispersion slope of DSF or NZ-DSF at 1.55 m band, and
to compensate for the dispersion of various fiber transmission lines having various
dispersion values and variation of dispersion value caused by the temperature change
or the like. WDM signals distorted by the dispersion slope of the fiber are introduced
into an input waveguide, and are demultiplexed by a wavelength demultiplexer into
each wavelength component, and pass through lattice-form optical circuits, transversal-form
optical circuits, or the combination of these circuits. The dispersion slope of
the signals is compensated for by these circuits. The recovered signals are multiplexed
by a wavelength multiplexer, and the multiplexed light is outputted at an output
waveguide. Arrayed-waveguide gratings can be used as the wavelength demultiplexer
and multiplexer. Also, cascaded configuration of Mach-Zehnder interferometers,
bulk-type optical filters, or fiber-type (or waveguide-type) gratings in series
can also be used as the wavelength demultiplexer and multiplexer.
