This effectively eliminates the need to stock/maintain fixed
wavelength transponder (sparing) packs, lowering overall operations costs. This
is a key point given that laser transponders tend to dominate DWDM economics.
Moreover, market pressures and cost innovations have allowed full-band tunable
lasers to be priced at nominal premiums over their fixed counterparts [2].
?– Optical amplifiers The development of wideband optical amplifiers has been
another key driver of DWDM growth, most notably C- and L-band erbium-doped fiber
amplifiers (EDFA) [1]. These devices deliver vast improvements in span lengths
and curtail the need for costly per-channel electronic (SONET/SDH) regeneration.
The net result has been a tremendous reduction in the cost-per-bit-per-mile. For
example, commercial EDFA solutions offer very good noise/gain flatness across the
C- and L-bands and increased 200??“600 km reach. In addition some vendors also offer
smaller, more cost-effective, subband EDFA devices to boost smaller wavelength
groups, i.e., amplets. Moreover, many new designs also feature fully integrated automatic
gain control (AGC) power balancing.
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