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I. INTRODUCTION
DWDM utilizes a large aggregate bandwidth in a single fiber
by taking advantage of advanced optical technology that is able
to launch and multiplex many wavelengths in one fiber, switch
wavelengths optically with channels having spacing of 0.8nm
or less, and at the receiving end, de-multiplex and read each
wavelength separately. In DWDM, each wavelength constitutes
a separate channel capable of carrying traffic at a bit rate that
may not be the same on all channels. DWDM systems take
advantage of advanced optical technology (e.g., tunable lasers,
narrowband optical filters, etc.) to generate many wavelengths
in the range around 1550 nm. ITU-T Recommendation 0.692
defines 43 wavelength channels, from 1530 to 1565 nm, with a
spacing of 1000Hz, each channel carrying an OC192 signal at
10 GbitsHowever, systems with wavelength channels of more
than 43 wavelengths have been introduced, and systems with
many more wavelengths are on the experimenter's workbench.
Currently, commercial systems with 16, 40, 80, and 128
channels (wavelengths) per fiber have been announced. Those
with 40 channels have channel spacing of 100 GHz, and those
with 80 channels have channel spacing at 50 GHz. This
channel separation determines the width of the spectral
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