Overall, the inherent transparency
of optical amplification facilitates the coexistence of multiple protocol types over a
single fiber-plant??”a huge advantage. Note that many researchers today are also
studying wider-band Raman amplification, albeit the costs are notably higher.
?– Filters Filtering plays a vital role in extracting individual DWDM wavelength
channels from SMF cables, i.e., multiplex, demultiplex, and bypass operations.
Currently, three key types of passive (or nonpowered) filtering technologies are
in use??”thin-film, planar waveguide, and fiber-gratings. Thin-film filters are ideal
for wider channel spacings (100, 200 GHz) and exhibit good temperature stability
and passband isolation. Meanwhile, increased C- and L-band densities and larger
channel counts can be achieved using planar waveguide devices such as arrayed
waveguide gratings (AWG) or fiber-grating filters. Examples include 40 channels
at 100 GHz/0.8 nm or 80 channels at 50 GHz/0.4 nm.
?– Optical switches All-optical switches are crucial for implementing spatial
interconnection in a dynamic manner, for example, for connection routing, protection,
and so on.
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